Asymmetric and general vibration waveforms from multiple synchronized vibration actuators

ABSTRACT

The disclosure relates to General Synchronized Vibration devices that provide haptic feedback to a user and improve the performance of existing vibratory devices. Different actuator types may be employed to provide synchronized vibration, including linear rotary actuators, rotating eccentric mass actuators including interleaved rotating mass actuators, and rocking mass actuators. A controller sends signals to one or more driver circuits to provide adjustment of vibration magnitude, frequency, and direction of the actuators. The system may apply forces onto an object, and a sensor measures a feature(s) of the object. This information is provided to a vibration device controller, which can then modify the vibration waveform to improve overall system performance. Fourier synthesis can be used to approximate arbitrarily shaped waveforms by controlling the phase and frequency of vibration actuators. These waveforms can include asymmetry where the peak force in one direction is higher than the peak force in another direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 13/030,663, filed Feb. 18, 2011, and entitled SYNCHRONIZEDVIBRATION DEVICE FOR HAPTIC FEEDBACK, which is a continuation of U.S.application Ser. No. 11/476,436, filed Jun. 27, 2006, issued on Apr. 5,2011 as U.S. Pat. No. 7,919,945, which claims the benefit of the filingdate of U.S. Provisional Patent Application No. 60/694,468 filed Jun.27, 2005 and entitled SYNCHRONIZED VIBRATION DEVICE FOR HAPTIC FEEDBACK,the entire disclosures of which are hereby expressly incorporated byreference herein. This application also claims the benefit of the filingdates of U.S. Provisional Patent Application No. 61/453,739, filed Mar.17, 2011 and entitled ASYMMETRIC AND GENERAL VIBRATION WAVEFORMS FROMMULTIPLE SYNCHRONIZED VIBRATION ACTUATORS, and of U.S. ProvisionalPatent Application No. 61/511,268, filed Jul. 25, 2011 and entitledASYMMETRIC AND GENERAL VIBRATION WAVEFORMS FROM MULTIPLE SYNCHRONIZEDVIBRATION ACTUATORS, the entire disclosures of which are herebyexpressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

Vibration devices are used in a wide range of applications includinghaptic displays, haptic interfaces, force feedback devices, vibratoryfeeders, beauty products, personal hygiene products, personal pleasureproducts, personal massagers, tree harvesters, and seismic vibrators.Some widely used products that include haptic displays include theDUALSHOCK® 3 wireless controller for Sony Computer Entertainment'sPlayStation® 3; the PlayStation® Move motion controller for motiongaming with Sony Computer Entertainment's PlayStation® 3; MicrosoftCorporation's Xbox 360 Wireless Speed Wheel; and the Wii Remoter™ Pluscontroller which is used for motion gaming with the Nintendo Wii.

Vibration actuators are typically the smallest and lowest cost methodfor generating haptic sensations. Therefore, it is advantageous to usevibration actuators to create a wide range of haptic sensations. Commonlow cost vibration actuators include Eccentric Rotating Mass actuators(ERMs) and Linear Resonant Actuators (LRAs). One of the advantages ofboth ERMs and LRAs is that they can generate relatively large vibrationforces from low power input. Both ERMs and LRAs generally build upkinetic energy during their ramp-up period; an ERM does this as thevelocity of its rotating mass increases, and an LRA does this as theamplitude of vibration of its moving mass increases. These low costactuators are used in many applications, including in consumerelectronics products such as smartphones and videogame controllers.

Many smartphones today use either a single ERM or a single LRA toproduce alerts by vibrating the entire device. This has the advantagethat the vibration alert can be felt while the device is inside aperson's pocket. Game controllers (also commonly termed interchangeablyas “videogame controllers” or simply “controllers”) often incorporatetwo ERMs within a two-handed device such as the Xbox 360 WirelessController or the Xbox 360 Wireless Speed Wheel (both devices fromMicrosoft). Sometimes such dual-ERM controllers are configured with oneERM having a large rotating mass and the other ERM having a smallrotating mass. A single-handed controller such as the Wii Remote™ Plus(from Nintendo) will typically have a single ERM to provide vibrationfeedback to the user.

A common limitation of most existing vibration devices is the inabilityto define the directionality of the vibratory forces. ERM actuatorsgenerate centripetal forces that rotate in a plane, and generally thedirection of vibration (that is to say, the instantaneous direction ofthe rotating centripetal force vector) cannot be not sensed in hapticapplications due in part to the high rate of change of the direction ofvibrations. In an ERM a centripetal force is applied onto the eccentricmass by the motor shaft, and an equal and opposite centrifugal force isapplied onto the motor shaft. In this document both the termscentripetal and centrifugal are used with the understanding that theseare equal but opposite forces. LRAs vibrate back and forth, and thus itmay be possible to sense the axis of vibration, but it is not possibleto provide more of a sensation in the forward direction relative to thebackward direction or vice versa. Since haptic applications are oftenintegrated with audio and video displays such as in computer gamingwhere directions are an integral component of the game, it is desirableto provide a haptic sensation that also corresponds to a direction.Moreover, it is be useful to generate haptic cues of directionality forapplications where a person does not have visual cues, such as to guidea vision-impaired person. Therefore, it is desirable to provide ahuman-perceptible indication of directionality in vibratory hapticdisplays and interfaces. In addition, it is advantageous to usevibration actuators to generate a wide range of vibration waveformsincluding both directional and non-directional waveforms.

There have been some haptic vibration devices that provide a sensationof vibration direction, but these prior implementations havedisadvantages. Specifically, asymmetric vibrations have been used togenerate a haptic sensation that is larger in one direction than theopposite direction.

However, existing asymmetric vibrators are complex, costly, or havelimited controllability. They tend to be bulky and have low powerefficiency. Tappeiner et. al. demonstrated a vibration device thatgenerated asymmetric directional haptic cues (Tappeiner, H. W.; Klatzky,R. L.; Unger, B.; Hollis, R., “Good vibrations: Asymmetric vibrationsfor directional haptic cues”, World Haptics 2009, Third Joint EuroHaptics Conference and Symposium on Haptic Interfaces for VirtualEnvironments and Teleoperator Systems), yet this device uses a highpower and an expensive 6-DOF magnetic levitation haptic device. Amemiyaet. al. (Tomohiro Amemiya; Hideyuki Ando; Taro Maeda; “KinestheticIllusion of Being Pulled Sensation Enables Haptic Navigation for BroadSocial Applications, Ch. 21, Advances in Haptics, pp. 403-414”)illustrated a device that also generates asymmetric vibrations forhaptic applications, yet this device uses a complex and large linkagesystem with 6 links and it appears that the direction of vibrationcannot be modified in real-time.

Another limitation of vibration devices that use ERMs is that theamplitude of vibration is dependent on the frequency of vibration, sincethe vibration forces are generated from centripetal acceleration of aneccentric mass. Some prior approaches have used multiple ERMs to controlfrequency and amplitude independently, but in the process also generateundesirable torque effects due to the offset between the ERMs.

SUMMARY OF THE INVENTION

It is desirable to produce not only haptic directional cues but also tobe able to render legacy haptic effects, so that a single gamecontroller could generate both new and existing sensations. Therefore,one aspect of this disclosure, and associated embodiments described inthis specification include vibration devices and methods of operatingthose devices employing low cost vibration actuators that use a lowamount of electrical power to generate asymmetric vibrations and tocontrol the direction of the vibration forces, as well as othervibration waveforms. The aspects described within this disclosureaddress these limitations through a design that can generate uniquedirectional haptic cues that can be controlled in all 360 degrees of aplane, as well as other vibration waveforms. To provide a wide range ofvibration effects it is desirable to be able to control the amplitudeand frequency independently. This disclosure describes a vibrationdevice that uses ERMs and allows independent control of vibration forceand frequency, without generating torque vibrations. Since no torqueeffects are created, the vibration force can be brought all the way downto zero, even when the ERMs are rotating. With this approach thevibration forces can be turned on and off without having to wait for theERMs to spin up to speed or spin down, and therefore allow vibrationforces to be turned on and off more quickly and effectively increase theresponsiveness of the vibration device.

The present disclosure overcomes the disadvantages and limitations ofknown vibration devices by providing means of generating asymmetric andgeneral waveform vibration profiles from multiple vibration actuators.These vibrations can apply a force vibration, torque vibration, or acombined force and torque vibration onto an object or onto the ground.Numerous embodiments and alternatives are provided below.

In accordance with an embodiment, a vibration device is provided. Thevibration device comprises multiple vibration actuators or mechanicaloscillators in which the phases and frequencies of the actuators arecontrolled and synchronized. The amplitude of vibration of each actuatormay also be controllable to provide a wider range of waveforms. Throughthis synchronization and control is it possible in some embodiments togenerate arbitrary shaped vibration waveforms, including asymmetricwaveforms that have higher peaks in one direction and lower peaks in theopposite direction. With this approach the advantages of asymmetricvibrations can be realized with low cost and low power vibrationactuators. Moreover, the direction of vibration can be controlled inmultiple degrees of freedom.

Many vibration actuators generate sinusoidal waveforms. Common low costvibration actuators include ERMs and LRAs. Pivoting actuators androcking actuators are less common, but are described in U.S. Pat. No.7,994,741, and can replace LRAs in many applications. Other types ofactuators that can generate vibrations, that is to say “VibrationActuators”, include voice coils, linear actuators, linear forceactuators, pneumatic actuators, hydraulic actuators, piezoelectricactuators, electrostatic actuators, electoactive polymers (EAPs),solenoids, ultrasonic motors, and motors that drive vibrating linkages.This disclosure combines multiple Vibration Actuators in a mannerwhereby the vibration waveforms from the Vibration Actuators aresuperimposed to generate a desired combined waveform.

In many embodiments multiple Vibration Actuators are mounted onto amounting platform (equivalently termed as a “base plate” or a“sub-frame” or a “housing”) so that the vibration forces from eachactuator are vectorially added together to generate a combined vibrationwaveform. A control method is used to control the phase and frequency ofeach of the Vibration Actuators. In some embodiments the amplitude isalso controlled. Furthermore, in some embodiments the method of Fouriersynthesis is used to select the desired phase, frequency, and amplitudeof each of the members of a set of sinusoidal waveforms to generate adesired combined vibration waveform. Indeed, with enough actuators it ispossible to approximate an arbitrary vibration waveform, including bothsymmetric and asymmetric vibration waveforms.

A single Vibration Actuator generates vibration forces, torque, or forceand torques. Many Vibration Actuators generate simple vibrationwaveforms such as sinusoidal waveforms. In this disclosure multipleVibration Actuators are configured such that they generate a combinedvibration waveform. In many embodiments multiple Vibration Actuators aresecured to a mounting platform such that force and torques fromindividual Vibration Actuators are vectorially added to generate acombined vibration force, torque, or force and torque. This mountingplatform can be held by a person, worn by a person or otherwise placedin contact with a person, attached to a person, attached to an object,or placed on a surface. In other embodiments the mounting platform is apart of a locomotion device the vibration forces generate propulsionforces.

Multiple Vibration Actuators can be synchronized together by controllingtheir frequency of vibration, and the relative phase of vibration. Insome cases, the amplitude of vibrations is also controlled. Thefrequency, phase, and amplitude of vibration can refer to thecharacteristics of vibration force, torque, or force and torquewaveforms. In many Vibration Actuators, including most LRAs and ERMs,vibration forces coincide temporally with the motion of a moving mass.With LRAs a mass oscillates back and forth. With an ERM, an eccentricmass rotates about an axis. Accordingly synchronization of VibrationActuators can also refer to the control of the frequency and phase ofthe motion of multiple moving masses, and in some cases the amplitudesof motion.

One category of waveforms that is specifically useful for hapticapplications is asymmetric waveforms. These waveforms generate peakforces, peak accelerations, or peak rate of change of force (“jerk”) inone direction that are larger than these peaks in the oppositedirection. Asymmetric waveforms can also apply to torque, or torque andforce waveforms. These waveforms can provide a haptic sensation thatcorresponds to a specific direction. In one example, two LRAs aremounted onto a mounting platform such that their force vectors arealigned with each other, which are defined as an LRA Pair. The frequencyof one LRA is set to twice the frequency of the other LRA in the pair.

The relative phase of vibration between the two actuators issynchronized such that in one direction the peaks of the two vibrationforces occur at the same time with the same sign and thus throughsuperposition with constructive (positive) interference combine toincrease the magnitude of the overall vibration force. In the oppositedirection the peaks of the two actuators occur at the same time but withopposite signs and thus through superposition with destructive(negative) interference partially cancel each other out and therebyreduce the magnitude of the overall vibration force. With this approach,a larger peak force is felt in one direction and a lower peak force isfelt in the opposite direction. The relative phase of vibration betweenthe two actuators can be changed so that the larger force of thecombined waveform switches sign and occurs in the opposite direction. Inhaptic applications, a higher peak force can be sensed as a moresignificant sensory input than a lower magnitude force that has a longerduration. Thereby, by creating larger peak forces in one direction thanthe opposite direction, a haptic cue can be generated in a desireddirection such as forwards and backwards.

In another example, a set of LRAs is mounted onto a mounting platform inan orientation such that the LRAs within the set have their forcevectors aligned with each other. Fourier waveform synthesis can be isused to select the phase, frequency, and amplitude of each LRA toapproximate a desired vibration waveform. One example waveform is aSawtooth waveform, which creates a more sudden change of force in onedirection than the opposite direction. In this manner, the Sawtoothwaveform can be used to generate directional haptic cues. When thenumber of LRAs in a set is three, the Sawtooth waveform would begenerated with the first harmonic at relative amplitude of 1; the secondharmonic is at relative amplitude of ½; and the third harmonic with arelative amplitude of ⅓. Other waveforms can be generated from a set ofLRAs that generate high peak forces in one direction, and lower peakforce in the opposite direction.

In another example, two LRA pairs are mounted onto a mounting platform.The LRA pairs are oriented such that one of the LRA pairs is alignedwith an x-axis of a plane, and the second LRA pair is aligned with ay-axis of the same plane. The phase, frequency, and amplitude ofvibration of each LRA is controlled by a microprocessor, FPGA or othercontroller. In each LRA pair, one LRA is operated at twice the frequencyof the other LRA in the pair, so that an asymmetric vibration waveformcan be generated along the axis of each LRA pair. The frequencies of theLRA pair aligned with the x-axis are set equal to the frequencies of theLRA pair aligned with the y-axis.

By controlling the amplitude and phase of vibration of the LRA pairs itis possible, through vector superposition of the vibration forces, togenerate a combined vibration force that is aligned with an arbitrarydirection in the plane. In this fashion the direction of asymmetricvibrations can be independently controlled in all 360 degrees of aplane. In a similar embodiment, two LRA pairs are mounted onto amounting platform with their axes of force in the same geometric plane,but the two LRA pairs are not orthogonal to each other, as the x and yaxes are. Rather, the axes of the LRA pairs span the geometric plane ina linear algebra sense. Thus, even without orthogonally aligned pairs,asymmetric vibrations can be independently controlled in all 360 degreesof a plane.

In another example, three pairs of LRAs are mounted onto a mountingplatform with their axes of force oriented such that the three axes spanthe three dimensional space. In this fashion, asymmetric vibrations canbe arbitrarily generated in any 3D direction.

In another example, two LRA pairs are mounted onto a mounting platformwith the axes of both pairs aligned to a single axis. The two pairs arespaced a set distance apart to generate a desired torque effect. Bothpairs can be controlled so that their forces occur simultaneous in thesame direction, thereby generating a net force on the mounting platform,but no net torque about a central point in the mounting platform. Withanother control approach the force from one pair can be synchronizedsuch that it is in the opposite direction of the other pair, therebygenerating a net torque onto the mounting platform. A further variationis to have each pair generate an asymmetric vibration waveform, so thatthe peak torque applied to the mounting platform is larger in onedirection than the other direction. In this fashion it is possible togenerate a haptic cue that provides a sense of rotational direction.This is an example of asymmetric torque vibration.

According to one aspect of the disclosure, a controller (e.g., amicroprocessor or FPGA) is used to synchronize the vibration of multipleVibration Actuators, and the controller implementation depends on thetype of vibration actuator being controlled. LRAs, rocking actuators,and pivoting actuators can use similar controllers and include anactuator driver that controls the voltage or current applied to theactuator. An LRA has a moving mass that translates back and forth and arestoring spring that centers the mass.

In a similar fashion, rocking actuators and pivoting actuators have amass with rotational inertia that rocks back and forth with a restoringspring that centers it. LRAs, rocking actuators, and pivoting actuatorstypically have a resonant frequency, and the actuator driver typicallyuses a sinusoidal or square wave profile. When the actuator driveroperates near the resonant frequency of the actuator, large vibrationforces can be generated. LRAs, rocking actuators, and pivoting actuatorscan by synchronized with open-loop controllers, with no need forsensors. A controller can generate a driving waveform for each actuatorat a desired frequency, phase, and amplitude.

The precision of a controller for synchronizing LRAs, rocking actuators,and pivoting actuators can be improved in a number of ways. The physicalproperties of the LRA, rocking actuator, or pivoting actuators generatea phase lag between the actuator driver waveform and the vibration forcewaveform generated by the actuator. This phase lag may vary based uponthe frequency at which the actuator is being driven. In addition, duringactuator ramp-up and changes in frequency, phase, or amplitude there canbe further discrepancy between the actuator driver waveform and thevibration force waveform.

The precision of the synchronization can be improved by characterizingthe actuator dynamics and phase lag and incorporating this informationinto the controller so that the vibration forces are synchronized in thedesired fashion. An additional method for improving the precision ofsynchronization adds a sensor that measures the motion of the movingmass or vibration force of each actuator, and uses closed-loop feedbackcontrol to correct the control signal in real-time. Many consumerproducts use MEMS sensors such as 3-axis accelerometers for motionsensing. It is possible to periodically characterize each of theactuators through an occasional calibration routine which drives each ofthe vibration actuators in turn with a known vibration test pattern andutilizes a motion sensing sensor to measure the resulting vibration.

Other embodiments use ERM actuators. An ERM employs a motor with aneccentric mass attached to a shaft that is connected to the motors'rotor, which rotates relative to the motor's stator that is attached toa motor housing. A single ERM generates a rotating centripetal force ina plane that is normal to the axis of rotation of its shaft. Someembodiments use ERM pairs, which consist of two ERMs with similarcharacteristics that are mounted on a mounting platform with their axesof rotation aligned. In some embodiments, the eccentric rotating massesof the two ERMs are controlled to counter-rotate relative to each otherat the same frequency.

When the ERMs in a pair are counter-rotating, superposition of thecentripetal forces yields a sinusoidal vibrational force along a linearaxis, which is defined as the force axis and is normal to the axis ofrotation of the ERMs. A controller or mechanical coupling (such as gearsor timing belts) can synchronize the speed of each ERM and the relativephase of rotation between the eccentric masses of the two ERMs in thepair. Synchronization of the phase controls the direction of the forceaxis of force generated by the pair. Accordingly, a synchronized ERMpair can generate a vibrational force along a linear axis, where thedirection of the force axis is controlled by the relative phase of theERMs. Increasing the rotational speed of a single ERM can increase themagnitude of its vibrational force. An ERM pair can also be controlledin a co-rotating mode where both eccentric masses rotate in the samedirection, and thereby generate a combined centripetal vibrationalforce. These centripetal forces can be used to generate legacy effectsthat emulate existing or historic game controllers. Co-rotating ERMs canalso be controlled to modify the magnitude of vibration forceindependently from the frequency of vibration.

One example described herein uses two ERM pairs mounted onto a mountingplatform, with the axes of rotation all four ERMs aligned in paralleldirections. One ERM pair is operated at twice the frequency of thesecond ERM pair. The phase of each ERM pair is controlled such that thedirections of the force axis of both ERM Pairs are aligned parallel witheach other. Furthermore, the timing of vibration is synchronized betweenthe two ERM pairs such that in one direction the peaks of the vibrationforces of both ERM pairs occur at the same time, and in the samedirection and thus through constructive interference combine to increasethe magnitude of the overall vibration force. In the first direction thepeaks of the vibration forces of both ERM pairs occur at the same time,but in opposite directions and thus through destructive interferencepartially cancel each other out and thereby reduced the magnitude of theoverall vibration force. With this approach an asymmetric vibration isgenerated since a larger peak force is generated in one direction and alower peak force is generated in the opposite direction. With thisembodiment the direction of asymmetric vibrations can be independentlycontrolled in all 360 degrees of a plane.

ERMs can be synchronized to generate a wide range of vibration waveformsusing Fourier synthesis, in a manner similar to the methods used withLRAs. The mass and eccentricity of the rotating mass of each ERM paircan be selected for the appropriate amplitude of force at a desiredfrequency. Alternatively, co-rotating pairs of ERMs can by synchronizedto control the amplitude of vibration force, without the restriction ofa fixed eccentricity of rotating masses. Multiple ERM pairs can bemounted on a mounting platform with the axes of rotations aligned.

In this configuration arbitrary waveform profiles can be approximated,and the direction of the force axis is controllable in the plane that isnormal to the axes of rotation of the ERMs. In other embodiments, ERMpairs can be mounted in orientations where the axis of rotation of oneERM pair is not aligned in parallel with the axis of rotation of asecond ERM pair. Furthermore, there are useful embodiments where thereare multiple ERMs that are activated where no two ERMs have parallelaxes of vibration nor orthogonal axes of vibration. An example of thiswould be four ERMs each mounted on a face of a tetrahedron. Byactivating various co-rotating and counter-rotating pairs of these ERMs,a variety of salient haptic effects can be achieved. With this approach3D vibrations can be generated. Synchronized vibration can also begenerated by combining both an ERM and an LRA actuator on a singlemounting platform.

Asymmetric waveforms can be generated with as few as two VibrationActuators. By using Fourier synthesis the fidelity of the waveform canbe increased to an arbitrary precision by adding additional actuatorsthat generate harmonics of the waveform. Thus, while an ERM pair or anLRA pair may be employed, one could also use ERM triads or ERM quads,LRA triads or LRA quads, and so forth.

Co-rotating pairs of ERMs can be controlled so the eccentric masses are180 degrees out of phase. With this approach, the overall vibrationforce will be significantly reduced. In this configuration, a gyroscopiceffect could be sensed and used to generate haptic effects. Generally ahaptic gyroscopic effect requires a large rotational inertia.

The typical control method used to synchronize ERM actuators differsfrom that of LRAs. For synchronization it is necessary to control thefrequency and phase of the ERMs. Most existing ERM actuators arecontrolled in on-off operation or low precision speed control, and arenot synchronized in their phase. One method to control the frequency andphase of an ERM is to use a position sensor such as an encoder orpotentiometer on the shaft of the motor. Feedback control can be used toachieve the desired synchronization, but the added cost of the positionsensor is undesirable.

A component employed in accordance with aspects of this disclosure is alow cost frequency and phase sensor, which can be used to synchronizeERMs. In one embodiment, the frequency and phase sensor detects when therotating mass passes by. The sensor may be an optical reflective sensor,optical pass-through sensor, hall-effect sensor, or other type ofsensor. A microprocessor or other controller can track the time at whichthe rotating mass of each ERM passes by. The interval between successivetimes the mass rotates by the sensor is used to calculate the frequencyof rotation. Multiple sensor measurements can be used to increase theresolution of the sensor. In addition, a state observer can be used topredict the position of the eccentric mass in intervals between sensormeasurements. The relative time between sensors on different ERMs isused to measure the relative phase of each ERM. With the information offrequency and relative phase of each ERM, the controller can speed up orslow down each ERM to achieve the desired synchronization. Anothermethod, as previously, mentioned, is to use a MEMS accelerometer thatmay have a primary use of motion sensing for a consumer device—yet alsohave a secondary use to characterize and calibrate the ERMs and LRAs.

According to another aspect, a motor driver may be used to control thevoltage or current applied to each ERM. The motor driver can rotate themotor in a single direction, or could be a bidirectional motorcontroller such as an H-Bridge. When a bidirectional motor controller isused, reverse voltage can be applied to an ERM to slow it down morequickly and thus allow for faster adjustment to synchronizationrequirements. In addition, when a bidirectional motor controller is usedan ERM Pair can be operated both as in counter-rotating directions andin co-rotating directions. The co-rotating directions can generate alarge combined centripetal vibration force, and can be used to generatelegacy vibration effects to simulate non-synchronized ERM vibrations.

Synchronization of multiple Vibration Actuators can be used to generatea wide range of vibration effects. These include direction effects,gyroscopic effect, amplitude effects, and 2D and 3D effects.

According to one aspect of the disclosure, a vibration device comprisesa mounting platform and a plurality of actuators. Each of the pluralityof actuators is configured to build up an amplitude of that actuator'sforce output over successive cycles of operation. Each of the pluralityof actuators is attached to the mounting platform so the force outputsof the plurality of actuators are superimposed onto the mountingplatform. The plurality of actuators is configured to simultaneouslygenerate force waveforms, corresponding to the force outputs, for atleast two different harmonics of a desired force output waveform suchthat each actuator generates a single harmonic of the desired outputwaveform.

In one example, each of the plurality of actuators is selected from thegroup consisting of a linear resonant actuator, an eccentric rotatingmass actuator, a pivoting actuator, and a rocking actuator. In anotherexample, two of the plurality of actuators comprise interleavedeccentric rotating masses arranged so the two actuators are individuallycontrollable by a controller to simultaneously generate non-zero forceoutputs such that the superimposed force outputs of the two actuatorssum to substantially zero force and substantially zero torque.

In one alternative, the at least two different harmonics include a firstharmonic of the desired output waveform. In another alternative, the atleast two different harmonics include a second harmonic of the desiredoutput waveform. And in a third alternative, the at least two differentharmonics include a third harmonic of the desired output waveform.

According to one example, the vibration device further comprises acontroller coupled to the plurality of actuators to control an amplitudeof the desired output waveform. According to another example, thevibration device is configured to generate haptic directional cues.

In one alternative, the vibration device is arranged in a handheldelectronic device selected from the group consisting of a remotecontrol, a game controller, and a watch, and the vibration device isconfigured to generate one or more haptic effects for the handheldelectronic device. In this case, the game controller may be selectedfrom the group consisting of a driving game controller and a motion gamecontroller.

According to another aspect of the disclosure, a vibration devicecomprises a mounting platform, a plurality of eccentric rotating massactuators, and a controller. Each of the plurality of eccentric rotatingmass actuators is attached to the mounting platform. The controller iscoupled to the plurality of eccentric rotating mass actuators toindependently control a frequency and a phase of each eccentric rotatingmass actuator.

In one alternative, the plurality of eccentric rotating mass actuatorsincludes two pairs of eccentric rotating mass actuators. Each pair isaligned and attached to the mounting platform such that: the first pairof eccentric rotating mass actuators is configured to counter-rotate ata first rotational frequency f1 to produce a first linear vibratingforce, and the second pair of eccentric rotating mass actuators isconfigured to counter-rotate at a second rotational frequency f2 toproduce a second linear vibrating force, the second rotational frequencyf2 being an integer multiple of the first rotational frequency f1, sothat a combined linear vibration force waveform on the mounting platformgenerated by operation of the two pairs of eccentric rotating massactuators is asymmetric.

In one example, axes of revolution of each eccentric rotating massactuator of the two pairs of eccentric rotating mass actuators aresubstantially parallel. In another example, the two pairs of eccentricrotating mass actuators are controlled by the controller to generatecentripetal forces such that the first linear vibrating force, when thefirst pair is operating at the first rotational frequency f1, issubstantially twice the second linear vibrating force when the secondpair is operating at the second rotational frequency f2.

In a further example, the axes of revolution of each eccentric rotatingmass actuator of the two pairs of eccentric rotating mass actuators arecollinear. In yet another example, centripetal force vectors of eacheccentric rotating mass actuator of the two pairs of eccentric rotatingmass actuators are coplanar. And in another example, the controller isconfigured to generate haptic directional cues using the two pairs ofeccentric rotating mass actuators.

According to another alternative, relative phases between the pluralityof eccentric rotating mass actuators are controlled by the controller tocancel out centripetal forces generated by each of the eccentricrotating mass actuators; and torques generated by the centripetal forcesby each of the eccentric rotating mass actuators cancel each other out.

In one example, a frequency, direction and relative phase between eachof the eccentric rotating mass actuators are controlled by thecontroller to produce a combined vibration force along a predeterminedaxis. In this case, the combined vibration force along the predeterminedaxis may be asymmetric.

In another example, the plurality of eccentric rotating mass actuatorsincludes a first eccentric rotating mass actuator and a second eccentricrotating mass actuator, the first and second eccentric rotating massactuators having the same eccentricity; and the controller is configuredto operate the first and second eccentric rotating mass actuators at thesame frequency and the same phase relative to other eccentric rotatingmass actuators in the plurality of eccentric rotating mass actuators.

In a further alternative, the plurality of eccentric rotating massactuators comprises a first eccentric rotating mass actuator having afirst axis of rotation, and a second eccentric rotating mass actuatorhaving a second axis of rotation, the first and second axes beingcollinear. The first eccentric rotating mass actuator has a firsteccentric mass with a center of eccentricity at a first positionprojected onto the first axis of rotation. The second eccentric rotatingmass actuator has a second eccentric mass with a center of eccentricityat a second position projected onto the second axis of rotation. Adistance between the first and second positions is substantially zero.

In another alternative, the plurality of eccentric rotating massactuators comprises a first eccentric rotating mass actuator having afirst axis of rotation, a second eccentric rotating mass actuator havinga second axis of rotation, and third eccentric rotating mass actuatorhaving a third axis of rotation, where the first, second and third axesbeing collinear. The first eccentric rotating mass actuator has a firsteccentric mass with a center of eccentricity at a first positionprojected onto the first axis of rotation. The second eccentric rotatingmass actuator has a second eccentric mass with a center of eccentricityat a second position projected onto the second axis of rotation. And thethird eccentric rotating mass actuator has a third eccentric mass with acenter of eccentricity at a third position projected onto the third axisof rotation. A distance between the first position and the secondpositions times the second eccentricity is equal to a distance betweenthe first position and the third position times the third eccentricity.In this case, the eccentricity of the first eccentric mass may be equalto the second eccentricity plus the third eccentricity.

In another aspect of the disclosure, a vibration device comprising amounting platform, a pair of linear resonant actuators arranged inparallel and attached to the mounting platform, and a controller. Eachlinear resonant actuator including a moveable mass. The controller iscoupled to the pair of linear resonant actuators. The controller isconfigured to control a first one of the linear resonant actuators toimpart a first sinusoidal vibration force of a first frequency f1 ontothe mounting platform, and to control a second one of the linearresonant actuators to impart a second sinusoidal vibration force of asecond vibration frequency f2 onto the mounting platform, the secondfrequency f2 being an integer multiple of the first frequency f1. Thecontroller is further configured to control amplitudes and phases of thefirst and second sinusoidal vibration forces to generate a combinedvibration waveform that is asymmetric.

In one example, the first and second linear resonant actuators are eachoperable over a range of frequencies including resonant frequencies ofthe second linear resonant actuators. In this case, the resonantfrequency of the second linear resonant actuator may be tuned to be aninteger multiple of the resonant frequency of the first linear resonantactuator.

In another example, the vibration device is configured to generatehaptic directional cues using the first and second linear resonantactuators. In a further example, the vibration device is configured toproduce haptic effects that correspond to one or more computer-generatedvisual events.

In yet another example, the vibration device is arranged in a handheldcontroller, and the vibration device is configured to generate effectsfor the handheld controller. In a further example, the vibration deviceis arranged in a device wearable by a user, and the vibration device isconfigured to generate haptic effects for the wearable device. And inyet another example, n the vibration device is part of a navigationdevice for navigating a user from waypoint to waypoint.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart illustrating a number of different waveform typessuitable for use with aspects of the present disclosure.

FIG. 2 illustrates a pair of vibration profiles having a phasedifference.

FIG. 3 illustrates a pair of in-phase vibration profiles.

FIG. 4 illustrates a linear motion vibration actuator for use withaspects of the present disclosure.

FIGS. 5A-B illustrate an example of a linear motion vibration actuatorin accordance with aspects of the present disclosure.

FIGS. 6A-B illustrate another example of a linear motion vibrationactuator in accordance with aspects of the present disclosure.

FIGS. 7A-B illustrate a further example of a linear motion vibrationactuator in accordance with aspects of the present disclosure.

FIGS. 8A-B illustrate yet another example of a linear motion vibrationactuator in accordance with aspects of the present disclosure.

FIG. 9 illustrates a further example of a linear motion vibrationactuator in accordance with aspects of the present disclosure.

FIG. 10 illustrates a vibration device in accordance with aspects of thepresent disclosure.

FIG. 11 illustrates the vibration device of FIG. 10 for generating acounterclockwise rotation in accordance with aspects of the presentdisclosure.

FIG. 12 illustrates the vibration device of FIG. 10 for generating aclockwise rotation in accordance with aspects of the present disclosure.

FIG. 13 illustrates the vibration device of FIG. 10 for generating achange in the direction of force in accordance with aspects of thepresent disclosure.

FIG. 14 illustrates a vibration device employing non-orthogonal linearactuators in accordance with aspects of the present disclosure.

FIG. 15 illustrates a vibration device employing a set of linearactuators for generation of a three dimensional force vector inaccordance with aspects of the present disclosure.

FIG. 16 illustrates a game controller in accordance with aspects of thepresent disclosure.

FIG. 17 illustrates a vibration device in accordance with aspects of thepresent disclosure.

FIG. 18 illustrates another vibration device in accordance with aspectsof the present disclosure.

FIG. 19 illustrates a vibration device for generating a combined torquein accordance with aspects of the present disclosure.

FIG. 20 illustrates another vibration device for generating a combinedtorque in accordance with aspects of the present disclosure.

FIG. 21 illustrates a rotary vibration actuator with eccentric mass inaccordance with aspects of the present disclosure.

FIG. 22 illustrates a vibration device with a pair of eccentric massactuators in accordance with aspects of the present disclosure.

FIG. 23 illustrates synchronous vibration of eccentric mass actuators inaccordance with aspects of the present disclosure.

FIGS. 24A-C illustrate a pivoting actuator in accordance with aspects ofthe present disclosure.

FIGS. 25A-C illustrate another pivoting actuator in accordance withaspects of the present disclosure.

FIG. 26 illustrates a pivoting actuator utilizing a pair of springdevices in accordance with aspects of the present disclosure.

FIGS. 27A-F illustrate a further pivoting actuator in accordance withaspects of the present disclosure.

FIG. 28 illustrates a synchronized vibration system employing rotaryactuators in accordance with aspects of the present disclosure.

FIGS. 29A-B illustrate game controllers in accordance with aspects ofthe present disclosure.

FIG. 30 illustrates a rocking actuator in accordance with aspects of thepresent disclosure.

FIG. 31 illustrates a vibration system in accordance with aspects of thepresent disclosure.

FIG. 32 illustrates control of a vibration system in accordance withaspects of the present disclosure.

FIG. 33 illustrates control of a vibration system in accordance withaspects of the present disclosure.

FIG. 34 illustrates control of a vibration system in accordance withaspects of the present disclosure.

FIG. 35 illustrates a vibration system in accordance with aspects of thepresent disclosure.

FIGS. 36A-B illustrate equation parameter and pattern selectionprocessing in accordance with aspects of the present disclosure.

FIG. 37 illustrates a haptic interface system in accordance with aspectsof the present disclosure.

FIG. 38 illustrates another haptic interface system in accordance withaspects of the present disclosure.

FIG. 39 illustrates control of vibration profiles in accordance withaspects of the present disclosure.

FIG. 40 illustrates a vibration actuator in accordance with aspects ofthe present disclosure.

FIG. 41 illustrates another vibration actuator in accordance withaspects of the present disclosure.

FIG. 42 illustrates a vibration device controller in accordance withaspects of the present disclosure.

FIG. 43 illustrates a vibration device with two linear resonantactuators for use with aspects of the disclosure.

FIG. 44 illustrates superposition of two synchronized sine waves with aphase offset that generates a combined waveform with asymmetry accordingto aspects of the disclosure.

FIG. 45 illustrates time steps within a vibration cycle of two linearresonant actuators generating an asymmetric waveform according toaspects of the disclosure.

FIG. 46 illustrates two linear resonant actuators directly attached toone another for use with aspects of the disclosure.

FIG. 47 illustrates an alternative example of two linear resonantactuators attached in line with one another for use with aspects of thedisclosure.

FIG. 48 illustrates a vibration device that uses a slider-crank linkagefor use with aspects of the disclosure.

FIG. 49 illustrates a vibration device with n LRAs for use with aspectsof the disclosure.

FIG. 50 illustrates an asymmetric pulse train according to aspects ofthe disclosure.

FIG. 51 illustrates a pulse train with zero DC according to aspects ofthe disclosure.

FIG. 52 is a flow diagram illustrating a process for maximizingasymmetry according to aspects of the disclosure.

FIG. 53 illustrates an example of waveform asymmetry according toaspects of the disclosure.

FIG. 54 illustrates another example of waveform asymmetry according toaspects of the disclosure.

FIG. 55 illustrates a further example of waveform asymmetry according toaspects of the disclosure.

FIG. 56 illustrates synchronized triangular waveforms according toaspects of the disclosure.

FIG. 57 illustrates a vibration device that can generate asymmetrictorques according to aspects of the disclosure.

FIG. 58 illustrates a controller for General Synchronized Vibration of apair of linear force actuators according to aspects of the disclosure.

FIG. 59 illustrates a linear force actuator with a sensor that detectswhen a moving mass passes a midpoint position according to aspects ofthe disclosure.

FIG. 60 illustrates a sensor attached to a mounting platform accordingto aspects of the disclosure.

FIG. 61 illustrates a vibration device controller that uses sensormeasurements to update a commanded amplitude, phase and/or frequencyaccording to aspects of the disclosure.

FIG. 62 illustrates a vibration device that includes two orthogonal setsof LRAs according to aspects of the disclosure.

FIG. 63 illustrates a vibration device that includes two non-orthogonalsets of LRAs according to aspects of the disclosure.

FIG. 64 illustrates an ERM for use with aspects of the disclosure.

FIG. 65 illustrates a vibration device using an arbitrary number of ERMsaccording to aspects of the disclosure.

FIG. 66 illustrates a vibration device having 4 ERMs for use withaspects of the disclosure.

FIG. 67 illustrates time steps within a vibration cycle of ERMsgenerating an asymmetric waveform according to aspects of thedisclosure.

FIG. 68 illustrates an example vibration device with a plurality of ERMpairs.

FIG. 69 illustrates a vibration device with four vertically stacked ERMsin one example used according to aspects of the disclosure.

FIG. 70 illustrates time steps of an asymmetric waveform for a vibrationdevice with four ERMs that are vertically stacked, according to aspectsof the disclosure.

FIG. 71 illustrates a vibration device with two ERMs that rotate in thesame direction.

FIG. 72 illustrates a vibration device with four co-rotating pairs ofERMs according to aspects of the disclosure.

FIGS. 73A-B illustrate vibration devices with two ERMs mounted indifferent arrangements according to aspects of the disclosure.

FIG. 74 illustrates an eccentric mass configured for use as a reactionwheel according to aspects of the disclosure.

FIG. 75 illustrates an ERM pair with interleaved masses according toaspects of the disclosure.

FIGS. 76A-B illustrate example configurations having three ERMs for usewith aspects of the disclosure.

FIG. 77 illustrates another configuration with three ERMs arranged in arow.

FIG. 78 illustrates an ERM with a sensor for use with aspects of thedisclosure.

FIG. 79 illustrates an ERM with a reflective optical sensor for use withaspects of the disclosure.

FIG. 80 illustrates an ERM with a line of sight sensor for use withaspects of the disclosure.

FIG. 81 illustrates an ERM with a Hall effect sensor for use withaspects of the disclosure.

FIG. 82 illustrates a vibration device with four ERMs arranged in a rowfor use with aspects of the disclosure.

FIG. 83 illustrates time steps of a waveform with cancellation of forcesaccording to aspects of the disclosure.

FIG. 84 illustrates a vibration device with two pairs of ERMs that sharethe same center.

FIGS. 85A-B illustrate an ERM pair with interleaved masses havingvarying thickness according to aspects of the disclosure.

FIGS. 86A-C illustrate an ERM pair with interleaved masses havingsupport bearing according to aspects of the disclosure.

FIG. 87 illustrates haptic feedback within a system having a visualdisplay according to aspects of the disclosure.

FIG. 88 illustrates another example of haptic feedback within a systemhaving a visual display according to aspects of the disclosure.

FIG. 89 illustrates a vibration device with sensor feedback according toaspects of the disclosure.

FIG. 90 illustrates a locomotion device for use with aspects of thedisclosure.

DETAILED DESCRIPTION

The foregoing aspects, features and advantages of the present disclosurewill be further appreciated when considered with reference to thefollowing description of preferred embodiments and accompanyingdrawings, wherein like reference numerals represent like elements.

As used herein, an actuator is a device that can generate mechanicalmotion or force. Actuators can convert a source of energy intomechanical motion or force. The source of energy can be electrical,pneumatic, hydraulic, or another source. Examples of actuators includerotary and linear motors. Examples of electric actuators include DC, AC,and stepper motors.

The term “direction” includes the orientation of an axis, also referredto as vector direction. A vector aligned with a specific direction canbe either in the positive direction along the axis or the negativedirection along the axis. As used herein, the term direction maydistinguish between all angles in a circle, such as 0 to 360 degrees.And vibration control may distinguish between positive and negativedirections along a single axis. Furthermore, the term “controller” isused herein in some situations to reference to game controller, and inother situations to a real-time controller of actuators, such as amicroprocessor or an ASIC.

In this disclosure, the term “General Synchronized Vibration” refers tocontrol of the timing, and in some cases also control of amplitude, ofmultiple vibration forces, torques, or forces and torques. The sourcesof these vibration forces and torques can be electromagnetic,electrostatic, magnetic, spring forces, inertial forces such ascentripetal forces, piezoelectric, pneumatic, hydraulic, or other forceand torque sources. The sources of these vibration forces and torquescan include those described in the text “Engineering Haptic Devices: ABeginner's Guide for Engineers” by Thorsten A. Kern, © 2009 (the entiredisclosure of which is hereby expressly incorporated by referenceherein). These vibration forces and torques can be generated fromseparate Vibration Actuators or from actuators that generate multipleforce, torques, or forces and torques. In General Synchronized Vibrationthe forces, torques, or forces and torques are vectorially combined sothat they generate a combined force, torque, or force and torque onto anobject. The vector combination of force and torque vectors is alsoreferred to as superposition. General Synchronized Vibration results ina combined vibration force, a combined vibration torque, or a combinedvibration force and vibration torque onto an object. A force appliedonto an object can also apply a torque onto that object. Accordingly,the references in this document to force also apply to force and torqueunless explicitly described otherwise.

In the event that there is a difference in the usage of terminologybetween the instant application and any wholly included referenceidentified herein, the usage of the differing term definitions will begoverned by the use in the present disclosure.

A vibration (or vibratory) actuator can impart repeated forces onto anobject. These repeated forces can repeat a similar force profile overtime during each repetition. Examples include rotary motors witheccentric masses, and linear actuators which move masses back and forth.These actuators can be DC, AC, stepper, or other types of actuators. Avibration actuator can repeat a similar force profile (waveform) in eachcycle, or there can be variations in force profiles between cycles.Variations between cycles can be in amplitude, frequency, phase, andprofile shape.

When a force is generated in a repeated cycle it can generate avibratory force. The profile (also referred to as a waveform) of arepeated force cycle can be in a sinusoidal shape, triangular wave, asquare wave, or other repeated profile as shown in FIG. 1. The frequencyof vibration describes how frequently a vibration cycle is repeated. Afrequency of vibration, f, is defined as the number of vibrations perunit time, and often is given in Hertz whose units are cycles persecond. The period of vibration, T, is the duration of each cycle inunits of time. The mathematical relationship between frequency andperiod of vibration is given by the following equation:f=1/T  (1)

A vibration force, F, is in a repeated cycle whenF(t+T)=F(t)  (2)where T is the period of vibration and t is time.

For purposes of vibration devices it is sufficient for the period ofvibration to be approximate, and therefore a vibration is considered tobe in a repeated cycle when:F(t+T)≈F(t)  (3)

One vibration waveform is a sinusoidal waveform, where the vibrationforce can be given by:F(t)=A sin(ωt+φ)  (4)

Here, F(t) is force as a function of time. A is the maximum amplitude offorce. ω is the frequency of vibration in radians per second (thefrequency in Hertz is f=ω/(2π)). And φ is the phase of vibration inradians. When ωt=2π the force profile repeats itself.

A vibration actuator may impart repeated forces onto an object. Due tothe dynamics of an actuator, a single actuator can impart forces atmultiple frequencies at the same time. However, for the purposes ofanalyzing vibrations and describing vibration devices herein, theprimary frequency of an actuator's motion means the frequency having thelargest component of kinetic energy in it.

The period of vibration can be defined by the time elapsed between thebeginning of one vibration cycle and beginning of the next cycle. Thusto identify the period of vibration it is useful to identify thebeginning of a cycle. One method for defining the beginning of cycle isto define the beginning of the cycle as the point with maximum amplitudein the profile. FIG. 1 is an amplitude versus time chart 10 showing thevibration profiles of a sine wave 12, a triangle wave 14, an arbitrarilyshaped profile 16, and a square wave 18. The period for each of theseprofiles is designated by T.

The sine wave 12, triangle wave 14, and arbitrary profile wave 16 allhave a unique point of maximum amplitude during each repeated cycle, andthis point of maximum amplitude is used to define the beginning of thecycle. The square wave 18 does not have a unique point of maximumamplitude within a cycle; in such cases a repeated point on the profilecan be selected to designate the beginning of the cycle. In FIG. 1, thepoint at which the square wave 18 transitions from a low value to a highvalue is designated at the beginning point of the cycle, and used use todefine the period of the repeated profile. Thus, any profile that can berepresented as repeated cycles can represent a vibration.

A frequency of vibration can also be identified when the shape of signaldoes not consist of exactly repeated profiles. Variations in amplitudeof the cycle and small changes in the shape of a cycles profile stillallow one to identify a unique point that designates the beginning ofthe cycle. As long as a repeated point in the profile can be identified,then the beginning of each cycle, a vibration period, and vibrationfrequency can be determined.

The phase of vibration defines the timing of the beginning of a cycle ofvibration. A phase difference between two vibration waveforms is definedas the difference between the beginning of a vibration cycle in onewaveform and the beginning of a vibration cycle in the other waveform.If there is a nonzero difference in the phase of vibration between twoprofiles, then the beginning of the cycles do not coincide in time. FIG.2 is an amplitude versus time chart 20 showing two vibration profiles,22 and 24, with a phase difference Δ between them. The phase differenceΔ can be given in units of time, such as shown in FIG. 2. Alternatively,the phase of vibration can also be given in radians for sinusoidalvibrations. When the phase difference Δ between two waveforms is zero,then the two waveforms are considered to be in-phase, as shown in theamplitude versus time chart 30 of FIG. 3.

As long as it is possible to identify the beginning of a cycle it ispossible to identify a phase of vibration, even when the amplitude andfrequency of vibration change between cycles of vibration.

One implementation of synchronized vibration is a vibration force formedby the superposition of two or more vibration waveforms where each ofthe waveforms include peaks that coincide in time with the peaks of theother waveforms on a regularly repeating basis. In a preferredembodiment, each of the waveforms would have the same frequency and aspecified phase difference between them. Superposition can preferably bethe vector sum of forces, torque, or forces and torque. Typically, thesources of these vibration waveforms are different vibration actuators.Often in synchronous vibration the waveforms have a zero phasedifference between them, and thus the vibration waveforms are in-phaseand in synchronous vibration. As used herein, specified phase differencemay range between and including 0° and 360°. In some embodiments, thespecified phase difference is 0° or 180°. In synchronized vibration, thevarious vibration waveforms can have different amplitudes. FIG. 3illustrates two vibration waveforms of triangular profile that aresynchronized. Both of these waveforms have the same frequency, they havedifferent amplitudes, and the waveforms are in-phase. The maximumamplitude of both waveforms in FIG. 3 occurs at the same time.

Typically, synchronized vibration profiles will have similar shapedprofiles. However, vibration actuators with different shaped vibrationprofiles can also be vibrated synchronously by matching frequency ofvibration and specifying the phase difference between the waveforms. Thematching of phase and frequency of vibration can be done approximatelyand still result in synchronized vibration.

Synchronized vibration can be generated by adding two vibration profilestogether, where the amplitude of the second vibration profile is amultiple of the amplitude of the first vibration profile. Thismultiplying factor can be either positive or negative.

If there are two or more vibrating actuators where the peak amplitude offorce of each vibrating actuator occurs repeatedly at approximately thesame time, then these actuators are in-phase and in synchronousvibration. The peak amplitude of force can be either in the positive ornegative direction of the vibration actuators' or vibration device'scoordinate system. Thus if a positive peak amplitude from one actuatoroccurs at approximately the same time as the negative peak amplitude ofanother actuator, then these actuators are in-phase and are insynchronous vibration.

An exemplary linear motion vibration actuator 100 is shown in FIG. 4. Asshown, the linear motion vibration actuator 100 contains a moving mass102 and a base 104. The moving mass 102 moves relative to the base 104in a back and forth linear motion. Force can be applied from the base104 to the moving mass 102 and in a similar fashion from the moving mass102 onto the base 104. The force transfer can occur, for instance, viamagnetic forces, spring forces, and/or lead screw forces. Examples oflinear actuators suitable for use in accordance with the presentdisclosure are described in U.S. Pat. Nos. 5,136,194 and 6,236,125, andin U.S. patent application Ser. No. 11/325,036, entitled “VibrationDevice,” the entire disclosures of which are hereby incorporated byreference herein.

As the moving mass 102 in the linear motion vibration actuator 100 movesback and forth, forces are generated between the moving mass 102 and thebase 104. These forces can be transmitted through the base 104 of theactuator 100 to an object that the actuator is mounted to (not shown).The moving mass 102 may also be attached to an object, such as a handle(not shown), that is external to the actuator 100, and may transmitforces directly to an object external to the actuator 100.

The forces in the linear motion vibration actuator 100 may be magneticforces, such as with a voice coil. The moving mass 102 may contain, forinstance, a permanent magnet, electromagnet, ferromagnetic material, orany combination of these. The base 104 may contain, for instance, apermanent magnet, an electromagnet, ferromagnetic material, or anycombination of these. Magnetic forces may be generated between base 104and the moving magnet that generate acceleration and motion of themoving mass 104. A force in the linear motion vibration actuator 100generated with an electromagnet can be modulated by controlling thecurrent flowing through the electromagnet.

One embodiment of linear motion vibration actuator 100 in accordancewith the present disclosure is shown in FIGS. 5A-B as linear motionvibration actuator 110. Actuator 110 preferably contains a moving mass112 that comprises an electromagnet, as well as a permanent magnet 116attached to the base 114. The motion of the moving mass 112 is along thex axis as shown in the side view in FIG. 5A. The magnetization polarityof the permanent magnet 116 is along the x axis as shown by the Northand South poles on the permanent magnet 116. The electromagnet ispreferably configured as a coil wound about the x axis. As shown in theend view of FIG. 5B, in the present embodiment the shape of theelectromagnet is desirably cylindrical and the shape of the permanentmagnet 116 is desirably tubular, although the electromagnet and thepermanent magnet 116 may have any other configuration. In thisembodiment both the electromagnet and the permanent magnet 116 may haveferromagnetic material placed adjacent to them to increase the forceoutput of the actuator 110.

In this embodiment, the force in the actuator 110 can be modulated bycontrolling the current in the electromagnet. When the current in theelectromagnet flows in one direction, then the magnetic force will pushthe moving mass 112 towards one side of the actuator. Conversely whenthe current in the electromagnet flows in the other direction, then themoving mass 112 will be pushed to the other side of the actuator 110.Increasing the amount of current in the electromagnet will increase theamount of force applied onto the moving mass 112.

Another embodiment of the linear motion vibration actuator 100 inaccordance with the present disclosure is shown in FIGS. 6A-B. Here,linear motion vibration actuator 120 preferably contains a moving mass122 that comprises a permanent magnet, as well as an electromagnetmagnet 126 attached to base 124. The motion of the moving mass 122 isalong the x axis as shown in the side view in FIG. 6A. The magnetizationpolarity of the permanent magnet is along the x axis as shown by theNorth and South poles on the permanent magnet. The electromagnet 126 ispreferably a coil wound about the x axis. As shown in the end view ofFIG. 6B, in this embodiment the shape of the electromagnet 124 istubular and the shape of the permanent magnet is cylindrical.

In this embodiment both the electromagnet 124 and the permanent magnetof the moving mass 122 may have ferromagnetic material placed adjacentto them to increase the force output of the actuator 120. The force inthe actuator 120 can be modulated by controlling the current in theelectromagnet 124. When the current in the electromagnet 124 flows inone direction, then the magnetic force will push the moving mass 122towards one side of the actuator 120. Conversely when the current in theelectromagnet flows in the other direction, then the moving mass 122will be pushed to the other side of the actuator 120. Increasing theamount of current in the electromagnet will increase the amount of forceapplied onto the moving mass 122.

Another embodiment of the linear motion vibration actuator 100 inaccordance with aspects of the present disclosure is shown in FIGS.7A-B, which is similar to the embodiment shown in FIGS. 6A-B. Here,actuator 130 includes a moving mass 132 and a base 134. The moving mass132 preferably comprises a permanent magnet. An electromagnet 136 atleast partly surrounds the moving mass 132. The electromagnet 136 isdesirably connected to the base 134. Unlike the actuator 120, theactuator 130 in this embodiment preferably includes one or more springs138 that are attached to the base 134 and to the moving magnet 132 ateither end, as shown in the side view of FIG. 7A. The springs 138 areoperable to generate forces in a direction that returns the moving mass132 to a center position, for instance midway between either end of theelectromagnet 136.

The springs 138 function to keep the moving mass 132 close to the centerposition when the actuator power is off, and to provide a restoringforce when the moving mass 132 is at one end of travel of the actuator130. The stiffness of the springs 138 can be selected so that thenatural frequency of the actuator 130 increases the amplitude ofvibration at desired natural frequencies. This spring effect can begenerated from a single spring, from a nonlinear spring, from extensionsprings, as well as compression springs. A number of such springconfigurations which may be employed with the present disclosure aredescribed in the aforementioned U.S. patent application Ser. No.11/325,036.

Another embodiment of the linear motion vibration actuator 100 accordingto aspects of the present disclosure is shown in FIGS. 8A-B. Thisembodiment is similar to the embodiments shown in FIGS. 6A-B and 7-B inthat actuator 140 includes a moving mass 142 including a permanentmagnet, a base 144, and an electromagnet 146 coupled to the base 144 andat least partly surrounding the moving mass 142. The electromagnet 146may be, e.g., rigidly or semi-rigidly coupled such that a vibrationforce is transmitted from the actuator 140 to the base 144, for instanceto enable a user to perceive the vibration force. In this embodiment, apair of permanent magnets 148 is attached to the base and are inoperative relation to the moving magnet 142 at either end as shown inthe side view of FIG. 8A. The permanent magnets 148 have poles, as shownby the N and S in FIG. 8A, which are configured to repel the moving mass142 and to generate forces in a direction that returns the moving mass142 to a center position. The permanent magnets 148 function to keep themoving mass 142 close to a center position when the actuator power isoff, and to provide a restoring force when the moving mass 142 is at oneend of travel of the actuator 140.

The size of the permanent magnets 148 attached to the base 144 can beselected so that the natural frequency of the actuator 140 increases theamplitude of vibration at desired natural frequencies. The actuator 140may be controlled so that one or more natural frequencies are selectedduring different modes or times of operation. Use of repulsive magneticforces as shown in FIG. 8A to generate centering forces on the movingpermanent magnet of the moving mass 142 can provide lower friction thanuse of springs 138 as shown in FIG. 7A, and thus can generate increasedactuator efficiency and smoothness. A number of configurations showinguse of permanent magnets to center a moving mass, which are suitable foruse in the present disclosure, are described in the aforementioned“Vibration Device” patent application.

Alternative embodiments of linear motion vibration actuators that mayalso be utilized with the present disclosure include both springs andmagnets, either alone or in combination, that return a moving masstowards the center of range of motion of the actuator.

A further alternative embodiment of the linear motion vibration actuator100 in accordance with the present disclosure is shown in FIG. 9. Thisembodiment comprises actuator 150, which is similar to a solenoid inthat it has a ferromagnetic moving plunger 152 for moving relative to abase 154. The plunger 152 is pulled into an electromagnetic coil 156when current flows through the coil 156. The coil 156 is coupled to thebase 154. A ferromagnetic end piece 158 can be located within or at theend of the coil 156 to increase the force output of the actuator 150. Aspring device 160 may be positioned opposite the end piece 158. Thespring device 160 is preferably employed to retract the plunger 152 outof the coil 156. As shown in FIG. 9, both an end of the coil 156 and anend of the spring 160 are desirably fixed to the base 154 of theactuator 150. The coil 156 and the spring 160 may be fixed to a singlebase at different sections thereon, or may be fixed to separate baseelements that are coupled together. The current in the coil 156 can beturned on and off to generate a vibration force.

A preferred embodiment of a vibration device 200 according to thepresent disclosure is shown in FIG. 10. In this embodiment, thevibration device 200 preferably includes two linear motion vibrationactuators mounted on to it, namely actuator 202 and actuator 204. Theactuator 202 includes a moving mass 206 and the actuator 204 includes amoving mass 208. The vibration actuators 202, 204 are attached to thevibration device 200 in a manner that transmits the force from thevibration actuators 202, 204 to the vibration device 200. Preferably thevibration device 200 has an enclosure or base (not shown) to which thevibration actuators 202, 204 are connected.

The vibration actuators 202, 204 are desirably attached in a relativelyrigid fashion to the vibration device enclosure or base. Rigidattachment provides a common base to the vibration device 200, uponwhich forces from both vibration actuators 202, 204 are applied. In thisembodiment, the two actuators 202, 204 are mounted at approximatelyright angles to each other. The force generated by actuator 202 is shownas force vector F₁, and the force vector from actuator 204 is shown asF₂. As expressed herein, vectors and matrices are designated by boldfont and scalars are designated without bolding. The combined forcegenerated by the vibration device 200 is the vector sum of the vibrationforces from both of the actuators 202, 204, and is shown in FIG. 10 asvector F_(combined).

The combined force, F_(combined), applied by the vibration actuators 202and 204 onto the vibration device 200 is a superposition of thevibration forces from each actuator, and is a function of time, t. Theforce vector can F_(combined)(t) is given by the vector equation:F _(combined)(t)=F ₁(t)+F ₂(t)  (5)where F₁(t) is the force vector from actuator 202 as a function of time,and F₂(t) is the force vector from actuator 204 as a function of time.

Both actuators 202, 204 can be operated in a vibratory fashion. For thecase of a sine wave vibration, the actuator forces can be given by:F ₁(t)=a ₁ A ₁ sin(ω₁ t+φ ₁)  (6)andF ₂(t)=a ₂ A ₂ sin(ω₂ t+φ ₂)  (7)respectively, where A₁ and A₂ are the respective amplitudes ofvibration, a₁ and a₂ are the unit vectors corresponding to therespective directions of vibration, ω₁ and ω₂ are the respectivefrequencies of vibration, φ₁ and φ₂ are the respective phase angles, andt is time. Other profile vibrations including square waves, trianglewaves, and other profiles can also be implemented with each actuator.

In the example shown in FIG. 10, actuator 202 is aligned with the yaxis, and thus the unit vector a₁ is represented by:

$\begin{matrix}{a_{1} = \begin{bmatrix}0 \\1\end{bmatrix}} & (8)\end{matrix}$and the unit vector a₂ aligned with the x axis and is represented by:

$\begin{matrix}{a_{2} = \begin{bmatrix}1 \\0\end{bmatrix}} & (9)\end{matrix}$The combined force vector, F_(combined), is given by the superpositionof forces form the actuators 202 and 204, and thus is given by:F _(combined)(t)=a ₁ A ₁ sin(ω₁ t+φ ₁)+a ₂ A ₂ sin(ω₂ t+φ ₂)  (10)

It is possible to vibrate actuators 202 and 204 shown in FIG. 10 in amanner that is in-phase and in synchronous vibration. Under suchvibration, there will be a single vibration frequency, ω and a singlephase φ Accordingly, F_(combined) can be given by:F _(combined)(t)=[a ₁ A ₁ +a ₂ A ₂] sin(ωt+φ)  (11)

With such in-phase and synchronous vibration the vibration issynchronized, then the peak forces from both linear motion vibrationactuators will occur at the same instances during each cycle ofvibration. The net direction of vibration force is the vectorcombination of [a₁A₁+a₂A₂]. Thus, in synchronized vibration and in-phasevibration, the vibration device generates a vibration force at aspecified frequency in a specified direction that results from thevector combination of forces from the direction and magnitude of each ofthe actuators in the device. It is possible to control the magnitude ofvibration in each linear motion vibration actuator, and thereby controlthe net direction of vibration of F_(combined).

In a preferred example, the vibration frequency, w, phase φ, andwaveform of each actuator are substantially identical. For instance, ω₂may be set to be substantially equal to ω₁ and φ₂ may be set to besubstantially equal to φ₁. By way of example only, ω₂ may be set towithin 10% of the value of ω₁, more preferably to within 5% of the valueof ω₁. Similarly, by way of example only, φ₂ may be set to within 10% ofthe value of ω₁, more preferably to within 5% of the value of φ₁. Inanother example, the frequencies and/or phases may be set exactly equalto one another. Alternatively, the frequencies, phases, and/or waveformsof each actuator may be set so that a user would not be able to noticethe difference in frequency, phase or waveform. In a furtheralternative, if the vibration device is used in a haptic application togenerate force sensations on the user, small variations may occur whichmay not be detected by the user or which cannot be significantly felt bythe user. In other instances, force sensations in a haptic applicationor in a vibratory feeder application may vary minutely so that userperformance in the haptic application or performance of the vibratoryfeeder is not significantly changed.

It is also possible to apply equation 11 to a vibration profile/waveformof arbitrary shape. Here, waveform p(t) may be used to represent thewaveform shape over time t. A period of vibration may be represented byp(t)=p(t+nT), where n=1, 2, 3, etc. and T is the period of vibration. Inthis case, an arbitrarily shaped synchronized vibration profile may berepresented as:F _(combined)(t)=[a ₁(t)A ₁(t)+a ₂(t)A ₂(t)]p(t)  (11.1)When the direction of vibration force for each actuator is substantiallyconstant relative to a base member, the arbitrarily shaped synchronizedvibration profile may be represented as:F _(combined)(t)=[a ₁ A ₁(t)+a ₂ A ₂(t)]p(t)  (11.2)

To illustrate how the direction of F_(combined) can be controlled, thepeak magnitudes, A₁ and A₂, are represented in FIGS. 10 and 11 by thelocation of the moving masses 206 and 208 within each of the actuators202 and 204, respectively. In FIG. 10, both actuator 202 and actuator204 are desirably vibrated at the same amplitude, and the correspondingF_(combined) is at approximately a 45 degree angle between the actuators202, 204.

By varying the magnitude of the vibration force in the actuators 202,204, it becomes possible to control the direction of vibration of thecombined force effect. In FIG. 11, the actuator 202 is vibrating at peakamplitude as illustrated by the peak position of moving mass 206 at theend of travel limits of actuator 202. However, actuator 204 is vibratingat a lower peak amplitude, as illustrated by the peak position of movingmass 208 closer to the middle of travel limits of actuator 204. Thelower peak force is also illustrated in FIG. 11 by the shorter lengthvector for F₂. The direction of the combined force, F_(combined), is theresult of vector addition of F₁ and F₂, and for vibrations illustratedin FIG. 11 is rotated counterclockwise relative to the direction shownin FIG. 10.

In a similar fashion, the direction of combined force can be rotated inthe clockwise direction as shown in FIG. 12. The vibration caseillustrated in FIG. 12 shows the peak amplitude of vibration of actuator202 reduced relative to that shown in FIG. 10, while the peak amplitudeof actuator 204 remains high. In this case, the vector addition of F₁and F₂ results in a clockwise rotation of F_(combined) in FIG. 12relative to the direction shown in FIG. 10.

It is also possible to change the direction of F_(combined) to anadjacent quadrant. As shown in FIG. 13, the sign of the F₂ has changedbe in the direction of the negative x axis, relative to the positive xdirection that shown in FIG. 10. The change in sign of F₂ can beachieved by changing the sign of A₂ in equation 11 above. It should benoted that one could achieve a similar representation of the combinedforce equation by defining actuator 204 vibration as at 180 degrees outof phase of actuator 202. However, changing the sign on the actuatorsvibration amplitude maintains the form of equation of synchronousvibration shown in equation 11. Thus, vibration that can be representedas 180 degrees out of phase can also be represented as in-phasevibration but with a negative amplitude of vibration.

An alternative embodiment of a vibration device in accordance with thepresent disclosure is shown in FIG. 14. Here, vibration device 210includes a first actuator 212 and a second actuator 214, havingrespective moving masses 216 and 218. FIG. 14 represents a twodimensional embodiment where two linear motion vibration actuators 212,214 are aligned with an xy plane. In this embodiment, it is notnecessary for the actuators 212, 214 to be orthogonal to each other. A₁and A₂ are respectively the amplitudes of vibration of actuators 212 and214, while a₁ and a₂ are respectively the unit vectors specifying thedirection of vibration of actuators 212 and 214.

The unit vector a₁ is given by:

$\begin{matrix}{a_{1} = \begin{bmatrix}{\cos(\alpha)} \\{\sin(\alpha)}\end{bmatrix}} & (12)\end{matrix}$where the angle α describes the orientation of actuator 1 relative tothe x axis as shown in FIG. 14. The unit vector a₂ is given by:

$\begin{matrix}{a_{2} = \begin{bmatrix}{\cos(\beta)} \\{\sin(\beta)}\end{bmatrix}} & (13)\end{matrix}$where the angle β describes the orientation of actuator 2 relative tothe x axis as shown in FIG. 14.

For a given vibration waveform the maximum magnitude of force vectors,F_(1, max) and F_(2, max), from actuators 212 and 214 in FIG. 14 can begiven by equations:F _(1,max) =A ₁ a ₁  (14)F _(2,max) =A ₂ a ₂  (15)

When actuators 212 and 214 are vibrated synchronously and in-phase (e.g.with the same frequency and with zero phase difference), then themaximum force amplitude occurs at the same time. Thus the maximumcombined force vector, F_(combined, max), is given though superpositionof the force vectors, and is given by:F _(combined,max) =F _(1,max) +F _(2,max)  (16)

A matrix of actuator directions, D_(L), can be created where each of itscolumns is a unit vector that corresponds to the direction of vibrationof a linear motion vibration actuator in a vibration device. For avibration device with two linear motion vibration actuators, such as theone shown in FIG. 14, the matrix D_(L) is given by:D _(L) =[a ₁ |a ₂]  (17)where a₁ and a₂ are column vectors.

A matrix representation of the combined force is given by:

$\begin{matrix}{F_{{combined},\max} = {D_{L}\begin{bmatrix}A_{1} \\A_{2}\end{bmatrix}}} & (18)\end{matrix}$where A₁ and A₂ are scalars. For the case of vibration in a plane, thevectors a₁ and a₂ will be 2×1 vectors and the matrix D_(L) will be 2×2.

When the direction matrix, D_(L), is invertible then the amplitude ofvibration in the individual actuators that corresponds to a desiredcombined force vector, F_(combined), is given by:

$\begin{matrix}{\begin{bmatrix}A_{1} \\A_{2}\end{bmatrix} = {D^{- 1}{Fcombined}}} & (19)\end{matrix}$

When the actuators are aligned orthogonally, then the direction matrix,D_(L), is orthonormal and its inverse is given by its transpose as shownbelow:D ⁻¹ =D ^(T)  (20)

When the direction matrix, D_(L), in not invertible because there aremore vibration actuators than directions of force being controlled, thena pseudo inverse of matrix D_(L) can be used. For example, if there are3 vibration actuators in the xy plane, and the control objective is onlyto control a two dimensional force, the D_(L) matrix is given by:D _(L) =[a ₁ |a ₂ |a ₃]  (21).where a₁, a₂, and a₃ are 2×1 column vectors.

The pseudo inverse is described in “Introduction to Linear Algebra”, 3rdEdition by Gilbert Strang, published in 2003 by Wellesley-CambridgePress, the entire disclosure of which is incorporated by referenceherein.

One method for calculating a pseudo inverse, D_(L) ⁺, is given by:D _(L) ⁺ =D _(L) ^(T)(D _(L) D _(L) ^(T))⁻¹  (22)

In such a case the amplitude of vibration for each actuator can be givenby:

$\begin{matrix}{\begin{bmatrix}A_{1} \\A_{2} \\A_{3}\end{bmatrix} = {D_{L}^{+}{Fcombined}}} & (23)\end{matrix}$

It is possible to specify the combined force vector, F_(combined), interms of a direction of vibration and amplitude. For a two dimensionalembodiment the combined amplitude of vibration can be specified by thescalar A_(combined), and the direction of vibration can be specified byan angle, theta, as shown in FIG. 14. In this two dimensional embodimentF_(combined) can be given by:

$\begin{matrix}{F_{combined} = {A_{combined}\begin{bmatrix}{\cos({theta})} \\{\sin({theta})}\end{bmatrix}}} & (24)\end{matrix}$

Thus, it can be seen that the amplitudes of vibration, A1 and A2, can berepresented in terms of the direction of vibration, theta, combinedamplitude of vibration, A_(combined), and direction matrix, D_(L), asgiven by:

$\begin{matrix}{\begin{bmatrix}A_{1} \\A_{2}\end{bmatrix} = {D_{L}^{- 1}{{Acombined}\begin{bmatrix}{\cos({theta})} \\{\sin({theta})}\end{bmatrix}}}} & (25)\end{matrix}$

Equation 25 provides the scalar magnitude of A₁ and A₂. When the sign ofA₁ is different than the sign of A₂ then vibration waveform can begenerated directly using the results of Eq. Avec. Alternatively, thewaveform can be generated using absolute values of A₁ and A₂ but withone waveform completely out of phase with the other waveform. A sinewave is defined to be completely out of phase when it is 180 degrees outof phase. General waveforms are defined to be completely out of phasewhen the maximum positive amplitude of vibration of one waveformconcedes with the maximum negative amplitude of the other waveform. Adepiction of two actuators vibrating completely out of phase is shown inFIG. 13. Two actuators vibrating completely out of phase are alsoconsidered to be in synchronized vibration.

It is also possible to specify the combined direction of vibration interms of a unit vector, a_(combined), as shown in FIG. 14. The vectorF_(combined) can be given by:F _(combined) =A _(combined) ×a _(combined)  (26)

Another configuration according to aspects of the present disclosure isa three dimensional configuration, where there are at least 3 linearmotion vibration actuators as shown in FIG. 15.

In the vibration device 220 of FIG. 15, actuators 222, 224 and 226 eachinclude a moving mass 228, 230 and 232, respectively. The actuators 222,224 and 226 are preferably orthogonal to each other and aligned with anxyz coordinate system. In an alternative three dimensional embodimentthe actuators are not necessarily orthogonal to each other; yet theforce vectors of the actuators span the three dimensional vector space.With such an alternative, an arbitrary direction of three dimensionalforce can be generated. In the three dimensional cases, the combineddirection of vibration can be specified by the 3×1 unit vector,a_(combined). The three dimensional combined force can be given by thesame equations for the 2 dimensional case, as shown belowF _(combined) =A _(combined) ×a _(combined)  (27)where a_(combined) and F_(combined) are 3 dimensional vectors.

Vibration devices according to the present disclosure may include anarbitrary number of actuators in arbitrary locations and orientations.

FIG. 16 illustrates a vibration device 240 having a pair of actuators242 and 244. The actuators 242 and 244 include moving masses 246 and248, respectively. In this embodiment, vibration device housing 250 isconfigured as a hand held game controller for computer or video games.Linear motion vibration actuator 242 is shown as being located in theleft handle and linear motion vibration actuator 244 is shown as beinglocated in the right handle. The actuators 242 and 244 need not beorthogonal, and need not be in the same plane.

Another alternative embodiment of a vibration device according to thepresent disclosure is shown in FIG. 17, where vibration device 260includes a first linear motion vibration actuator 262 and a secondlinear motion vibration actuator 264. As shown, the actuators 262, 264are located on top of each other. An advantage of such a configurationis that the actuators 262, 264 create little torque about the center ofthe vibration device 260, which may be desirable in some vibrationapplications.

In a variation of FIG. 17, FIG. 18 illustrates a game controller 270having two linear actuators, 272 and 274 disposed perpendicular to eachother. The actuators 272 and 274 are preferably rigidly mounted to case276 of a game controller. The actuators 272 and 274 could be mounted ina plane of any angle; however, they are preferably mounted in ahorizontal plane of the case 276. The actuators 272 and 274 do not haveto be located one on top of the other; rather they can be attached tothe same rigid body, such as the case 276 of a game controller. Ofcourse, one could attach three or more linear actuators to the case 276,preferably at right angles to each other to create force vectors thanspan the three dimensional space of the case 276. Moreover, theactuators do not have to be at right angles to each other. Desirably,the actuators are positioned relative to one another with differentorientations.

A further embodiment of a vibration device according to the presentdisclosure is shown in FIG. 19. Here, vibration device 280 includes twolinear motion vibration actuators, 282 and 284, which are aligned intheir orientation but separated by a distance D. Actuator 282 includesmoving mass 286 and actuator 284 includes moving mass 288. The actuators282, 284 may be vibrated such that the moving mass 286 in actuator 282is at a negative extreme along the y axis when the moving mass 288 inactuator 284 has a positive extreme along the y axis. In this fashionthe two actuators 282, 284 generate a combined torque when vibrated in asynchronous fashion. The embodiment shown in FIG. 19 could be operated,in one example, such that the moving masses 286 and 288 move in the samedirection when synchronized, and thereby generate a combined force alongthe y axis. In this fashion the configuration shown in FIG. 19 could beused to generate a combined torque, a combined force, or a combinationof force and torque.

An alternative embodiment of a vibration device 290 in accordance withaspects of the present disclosure is shown in FIG. 20. Here, threelinear motion vibration actuators 292, 294 and 296, each having a movingmass, are orientated on an xy plane. In this embodiment it is possibleto generate a combined force and a combined torque. It is also possibleto independently control the combine force and torque by modulating theamplitude of vibration in each of the actuators 292, 294 and 296. Thecombined torque and force are superpositions of the forces and torquesgenerated by each actuator. Since there are three actuators that can becontrolled independently, the components of the force along the x axis,the force along the y axis, and the torque about a selected point on thexy plane can all be modulated independently.

In the vibration device embodiments described herein the vibrationactuators may be attached to the vibration device in a rigid, asemi-rigid or a non-rigid fashion. Even when vibration actuators areattached in a non-rigid fashion to a vibration device, the vibrationdevice is operable to transmit the superposition of forces from allvibration actuators. When vibration actuators are attached in a rigidfashion to a vibration device, the combined force applied by thevibration device becomes less dependent on the location where thevibration device transmits force and torques to other bodies. Inaddition, the more rigid the attachment between the vibration actuatorsand the vibration device, the more uniform the timing of the forcesuperposition becomes at all points of the vibration device.

In an example, it is possible to attach the actuators directly onto aperson's hand and body, for instance as shown in U.S. Pat. Nos.6,275,213 and 6,424,333. In uses of the present disclosure whereactuators are directly attached or indirectly coupled to the hand orbody, the vibration force from each actuator may be felt directly atdifferent locations on the body, yet a synchronized combined forcevector can still be applied onto the body by synchronizing the operationof the actuators.

Vibration devices in accordance with the present disclosure can be builtwith rotary vibration actuators as well as with linear motion vibrationactuators. In some cases the cost to manufacture rotary vibrationactuators is less than the cost to manufacture linear motion vibrationactuators. Thus, if cost is a factor, it may be desirable to utilizerotary vibration actuators in place of or in combination with linearmotion vibration actuators. However, in order to generate synchronizedvibration with rotary vibration actuators, it is necessary to controlthe rotary position of the actuators along with the rotary velocity.

A rotary vibration actuator may comprise, for example, a DC motor, arotary solenoid, a rotary stepper motor, a servo motor, or other type ofrotary actuator. One advantage of rotary actuators is their relativelylow cost. The servo motor uses a position sensor and/or a velocitysensor for feedback. In some situations the rotary stepper motor may bemore desirable because it allows for control of position and velocitywithout the use of a sensor.

FIG. 21 shows a rotary vibration actuator 300 suitable for use with thepresent disclosure. The actuator 300 includes an eccentric mass 302coupled to a rotary actuator 304 along a shaft 306. As the rotaryactuator 304 is rotated, a centrifugal force is generated in the radialdirection aligned with the eccentric mass 302 as shown by the vector CFin FIG. 21.

Many existing vibrators utilize rotary vibration actuators witheccentric masses, but not with synchronized vibration. In accordancewith the present disclosure, a pair of rotary vibration actuators can beconfigured to achieve a vibration force that is aligned with a singledirection of motion. Accordingly, a pair of such rotary actuators can beused when a vibration force in a specified direction is required.

For instance, a vibration device according to the present disclosure canbe built, by way of example only, with two rotary vibration actuatorsthat rotate in opposite directions, as shown in FIG. 22. As shown, thevibration device 310 includes a pair of rotary vibration actuators 312and 314, each having an eccentric mass 316 and 318, respectively.Actuator 312 preferably rotates clockwise, and actuator 314 preferablyrotates counterclockwise. In the orientation shown the centrifugal forcevectors from both actuators are aligned with the y axis and superimposeto create a combined force vector, CVF, in the y direction.

With rotary vibration actuators it is possible to create synchronizedvibration in an analogous fashion to the synchronized vibrationdescribed with linear motion vibration actuators. With rotary vibratingactuators, synchronized vibration is defined to occur where two rotaryactuators rotate in approximately the same plane at the same angularvelocity in opposite directions, and where the relative angle betweenthe actuators is controlled, such that the actuator centrifugal forcevectors align repeatedly in the direction of desired vibration force.

The direction of vibration force can be controlled with a pair of rotary(or rocking) vibration actuators by controlling the angle at which thecentrifugal force vectors become aligned. Therefore, it is possible tocontrol the direction of combined force with rotary actuators in afashion analogous to how the direction of combined force can becontrolled with multiple linear vibration actuators.

FIG. 23 shows the embodiment of two rotary vibration actuators asdescribed with respect to FIG. 22, wherein the actuators are controlledin synchronized vibration for a number of positions. As shown in FIG.23, the combined force vector, CFV, remains in the y axis, and itsmagnitude changes according to the rotary position of the actuators. Themaximum combined force vector occurs when the centrifugal force fromboth rotary actuators are aligned.

An alternative type of rotary actuator suitable for use with the presentdisclosure is a rotary actuator with a pivoting mass. FIGS. 24A-Cillustrate respective front, side and bottom views of an exemplarypivoting actuator 400, which includes a mass 402 operable to pivotrelative to a rotary actuator 404. The mass 402 is connected to therotary actuator 404 via a shaft 406. The center of mass of the mass 402can be located anywhere on the body of the mass 402. Thus, the center ofmass may be concentric with the axis of rotation, or eccentric to theaxis of rotation. The pivoting actuator 400 may be configured tofunction in a manner similar to the rotary vibration actuators discussedabove.

As seen in FIGS. 25A-C, the rotary actuator 404 may be affixed to asupport 408, which, in turn, may connect to another object (not shown).Preferably a spring device 410 couples the pivoting mass 402 to asupport 412, which may be the same or a different support than thesupport 408. FIG. 25A illustrates the pivoting actuator 400 when thespring device 410 is in a rest state when the pivoting mass 402 is in acentral position.

The mass 402 may pivot in either a clockwise or counterclockwise manner.FIG. 25B illustrates counterclockwise operation. Here, the spring device410 is in a compressed state. In the present embodiment as shown, thespring device 410 is under a compression force that is primarily linearand is applied toward the right hand side of the figure. FIG. 25Cillustrates clockwise operation of the mass 402. Here, the spring device410 is in an uncompressed state in response to a force that is primarilylinear and is applied toward the left hand side of the figure.

Vibration forces and/or torques can be generated with the pivotingactuator 400 as shown in FIGS. 25A-C. The pivoting actuator 400 can beactivated to pivot the pivoting mass 402 first clockwise and thencounterclockwise, or vice versa. As the pivoting mass 402 rocks back andforth, the spring device 410 generates a vibration force, a torque, orboth a vibration force and torque onto the object to which it is affixedvia the support 408. In this fashion, if the pivoting mass 402 has acenter of mass concentric with the axis of rotation, the pivoting mass402 can be used to generate a vibration torque. Also in this fashion, ifthe pivoting mass 402 has a center of mass eccentric with the axis ofrotation, the pivoting mass 402 can be used to generate a vibrationforce.

Vibration forces and/or torques can be generated by moving a mass backand forth. It is possible to define the beginning of a vibrationwaveform as an instance at which a mass reverses its direction ofmotion. For linear actuators, the reversal of direction is a reversal oftranslation. For rotary actuators, the reversal of direction is areversal of rotation. In general, the reversal of motion of a mass in anactuator may include both translation and rotation.

In actuators having a spring device attached to a moving mass, energycan be built up in the spring device, especially when the mass is movedback and forth close to a natural frequency of the mass and springsystem. In such cases, the maximum vibration force can occur at themaximum deformation of the spring device, which can occur when the massreaches its maximum excursion and reverses its direction. Accordingly,moving masses in two (or more) actuators, that are operating insynchronized vibration, can reverse direction at approximately the sametime.

An alternative method for generating vibration would be to operate thepivoting actuator 400 in a clockwise (or counterclockwise) direction andthen deactivate the pivoting actuator 400 while allowing the springdevice 410 to rotate the pivoting mass 402 in the counterclockwise (orclockwise) direction. This approach would allow one to use pivotingactuators and control circuitry that only operates in a singledirection.

FIG. 26 illustrates a variation of the pivoting actuator 400, namelypivoting actuator 400′, which desirably includes the pivoting mass 402operable to pivot relative to the rotary actuator 404, and which isconnected thereto via the shaft 406. As above, the rotary actuator 404may be affixed to the support 408, which, in turn, may connect toanother object (not shown). Preferably a first spring device 410 acouples the pivoting mass 402 to a first support 412 a, and a secondspring device 410 b also couples the pivoting mass 402 to a secondsupport 412 b. The supports 412 a and 412 b may be a single support,separate supports that are physically connected, or physicallydisconnected supports. One or both of the supports 412 a,b may be thesame or a different support than the support 408.

One type of pivoting actuator 400 that could be employed is a DC motor.However, not all the components of the DC motor are necessary for thisapplication, because the output shaft does not rotate continuously.Accordingly it is not necessary to have motor brushes, which can reducecost as well as electrical power losses and frictional losses. In apreferred example, the pivoting actuator 400 may essentially include astator and a rotor. The stator may be stationary and desirably containspermanent magnets and/or electromagnets. The rotor is operable to pivotand can contain permanent magnets and/or electromagnets. The polarity ofthe magnets in the stator and rotor can be configured so that activationof the electromagnets causes an electromagnetic torque to be exertedonto the rotating mass 402.

In the embodiment of FIGS. 25A-C, the spring device 410 is configured tooperate in a generally linear fashion. However, In order to generatelarge magnitude of vibration forces with small actuators, it can beadvantageous to utilize the resonance of a system. The embodiments shownin FIGS. 25A-C have both a mass and a spring, and thus have a resonantfrequency. If the actuator is excited at or close to this resonantfrequency large amplitude vibrations can build up. However, it can bedesirable to operate the vibration device at a range of frequencies. Itis possible for a device to have a variable resonant frequency with useof nonlinear spring forces, as discussed in the aforementioned“Vibration Device” patent application. Accordingly, one could use anonlinear spring in the vibration device to achieve larger amplitude ofvibration over a range of frequencies.

It is possible to generate nonlinear spring force, even with use of alinear spring element. Consider the embodiment shown in FIG. 27A. Here,pivoting actuator 420 has a mass 422 operable to pivot relative to arotary actuator 424. The mass 422 is connected to the rotary actuator424 via a shaft 426. The rotary actuator 424 may be affixed to a support427, which, in turn, may connect to another object (not shown).Preferably a spring device 428 couples the pivoting mass 422 to asupport 427′, which may be the same or a different support than thesupport 427.

As shown in FIG. 27A, the spring device 428 is desirably placed in-linewith the pivoting mass axis. When the pivoting mass 422 is rotated asmall amount about the center position very little lengthening occurs inthe spring device 428. Accordingly, the effective spring constant is lowand the resonant frequency is low.

Low frequency operation is desirable in some situations, for instance ingames that have low frequency effects. For instance, games may generateactions or events in the sub-200 Hertz range, such as between 15 and 150Hertz. In certain cases the actions or events may be as low as 20-50Hertz or lower, such as about 10-20 Hertz. Examples of suchactions/events include gunshots, automobile related sounds such as a carspinning out of control, and helicopter related sounds such as thewhirring of the rotor blades. Eccentric mass actuators may not besuitable to generate a haptic sensation in this frequency range, butpivoting actuators or linear actuators may generate such frequencies.

As the magnitude of rotation of the pivoting mass 422 increases, thelengthening of the spring device 428 increases as shown in FIGS. 27B and27C. Accordingly, for larger amplitudes of rotation, the effectivespring constant is higher and the natural frequency of the system ishigher. In order to quickly ramp up the vibration amplitude when anonlinear spring force is used, the excitation frequency can be variedso that it always matches the natural frequency of the vibration device.

FIG. 27D illustrates a rotating actuator 430 having a rotating mass 432coupled to rotary actuator 434 via shaft 436. The rotary actuator 434 isdesirably coupled to a support 437, which, in turn, may connect toanother object (not shown). In this alternative, a spring device such asa torsion spring 438 is attached between the rotating mass 432 and therotary actuator 434. As shown, one end or tang 439 a of the torsionspring 438 is attached to the rotating mass 432, and the other end ortang 439 b is attached to the support 437 (or, alternatively, to therotary actuator 434 itself). Torsion spring 438 may be employed becausesuch spring devices permit a large degree of rotation of the rotatingmass 432 relative to the rotary actuator 434 and the support 437.

FIGS. 27E and 27F illustrate a further rotating actuator, namelyrotating actuator 440. The rotating actuator 440 includes a rotatingmass 442 having a slot 443 therein, a rotary actuator 444, and a shaft446 coupling the rotating mass 442 to the rotary actuator 444. Therotary actuator 444 is desirably coupled to a support 447, which, inturn, may connect to another object (not shown). In this embodiment apin 445 is held within the slot 443. A spring device 448 is coupled atone end or tang 449 a to the pin 445. The spring device 448 is coupledat the other end or tang 449 b to a support 447′. The support 447′ ispreferably different from the support 447, or, alternatively, ispreferably a different section of the support 447 from where the rotaryactuator is coupled.

FIG. 27E shows the spring device 448 in a “rest” position. FIG. 27Fshows the spring device 448 in a “compressed” position. Here, by way ofexample only, the rotating mass 442 may be rotating in a clockwisedirection. As the rotating mass 442 rotates, the pin 445 moves relativeto the slot 443, but the spring device 448 remains in substantially thesame orientation relative to the support 447′. In this fashion, theforce applied onto the fixed 447′ remains in relatively the samedirection as the moving mass 442 rotates. It is possible to incorporatea gap between the slot 443 and the pin 445 that would allow for somerotation of the shaft 446 before the spring device 448 is extended orcompressed from its rest position. The gap would create a non-linearforce effect on the rotating mass 442, which could aid in increasing themagnitude of vibration. The gap would allow the shaft 446 to morequickly reach higher speeds and for the rotating actuator 440 to morequickly build up rotating inertia.

While several types of actuators have been described above that may beused with the present disclosure, other types of actuators may also beemployed so long as they can be controlled as described herein. Forinstance, piezoelectric devices without separate or distinct “moving”and “stationary” masses may be employed either alone or in combinationwith other actuator types to impart vibratory forces in the mannersdescribed herein.

FIG. 28 illustrates a synchronized vibration system 450, which maycomprise two vibration devices 452 and 454, such as any of those ofFIGS. 24A-C, 25A-C, 26 and/or 27A-F. Of course, more that two vibrationdevices may be provided. The vibration devices 452 and 454 arepreferably mounted onto a base plate 456 in a generally orthogonalmanner as shown, although orthogonality is not required. The vibrationdevice 452 is preferably a horizontal vibrator that desirably has aspring device 458 which applies primarily horizontal forces onto thebase plate 456. The vibration device 454 is preferably a verticalvibrator that desirably has a spring device 460 that applies primarilyvertical forces onto the base plate 456. As long as the directions ofthe vibration forces of the different vibration devices are not aligned,it is possible to control the combined direction of vibration using thesynchronized vibration methods as described herein as well as in theaforementioned “Vibration Device” patent application.

An alternative embodiment of the present disclosure includes two rotaryvibration actuators whose planes of vibration are not the same; however,in this case the two planes are not orthogonal to each other. In thisembodiment, the component of centrifugal force from one actuator thatcan be projected onto the plane of the other actuator can be used toachieve a component of synchronous vibration.

In one example, two or more vibration devices may be mounted devicesinto a game controller, as shown in FIG. 29A. Here, a game controller470 includes a pair of vibration devices 472 and 474 mounted in both theright and left handles, respectively, of housing 476. The directions ofvibration of the vibration devices 472 and 474 are preferably notaligned, and thus it is possible to control the direction of vibrationusing the synchronized vibration approach discussed herein.

There are many orientations of both the rotary actuators and springsthat can be used to achieve an embodiment where synchronized vibrationis possible. For instance, the axis of rotation of both actuators can bealigned while the spring direction can vary, allowing an alternativeconfiguration for synchronized vibration. FIG. 29B illustrates a gamecontroller 480 having a pair of vibration devices 482 and 484 within ahousing 486 where the axes of the rotating shafts in both rotaryactuators are aligned, yet the spring forces are not aligned.

FIG. 30 illustrates yet another variation similar to the rotary andpivoting vibration devices. Here, a rocking actuator 490 preferablyincludes a rocking weight 492 rotatable about a shaft 494. Desirably,one end of the rocking weight 492 is operatively coupled via a firstspring device 496 a to a first support 498 a. The same end of therocking weight 492 is also desirably operatively coupled via a secondspring device 496 b to a second support 498 b. The supports 498 a and498 b may be a single support, separate supports that are physicallyconnected, or physically disconnected supports. The rocking actuator 490may be implemented in a device such as a game controller in any of theconfiguration described above.

A controller for synchronized vibration of a pair of rotary vibrationactuators specifies the angular position of each rotating shaft, suchthat the angle where the centrifugal force vectors are aligned is thedesired direction of force vibration and the angular position isincremented such that the rotational velocity matches the desiredvibration frequency.

A system 500 having a controller for one or more vibration devices thatuse linear motion vibration actuators is shown in FIG. 31. Vibrationdevice controller 502 specifies the desired vibration effect and one ormore driver circuit(s) 504 a, 504 b, . . . , 504N provide the necessarypower to actuators 506 a, 506 b, . . . , 506N. While each actuator 506is shown as being powered by a separate driver circuit 504, it ispossible for multiple actuators 506 to be driven by one driver circuit504.

The controller 502 may be, by way of example only, a microprocessor andthe driver circuit(s) 504 may be, for instance, one or more electricalamplifiers. The controller 502 and drive circuit 504 may be integratedinto a single microprocessor or single electrical circuit. The controlmethod in this figure is for a configuration with N actuators, where Nis an arbitrary number of actuators. Some of the figures showing variouscontrol methods in the instant application illustrate only twoactuators. However, it should be understood that control methodsaccording to the present disclosure can be extended to include anarbitrary number of actuators, as shown in FIG. 31.

FIG. 32 shows a control method for two actuators. Here the controller502 specifies the desired vibration amplitude, A, frequency, f, andphase, p, for each actuator 506. The amplitude, frequency, and phase ofactuator 506 a (A1, f1, p1) may differ from the amplitude, frequency,and phase of actuator 506 b (A2, f2, p2). The profile/waveform of thedesired vibration force may be a sine wave, square wave, triangle wave,or other profile, such as is discussed above with regard to FIG. 1. Theactual vibration profiles/waveforms of the actuators 506 a,b may differfrom the desired vibration profiles due the dynamics of the drivecircuits 504 a,b and actuators 506 a,b.

FIG. 33 shows a control method where the frequency of vibration, f, isthe same for both actuators 506 a,b. FIG. 34 shows a control methodwhere the frequency of vibration, f, and the phase of vibration, p, arethe same for both actuators 506 a,b. In this embodiment, the actuators506 a,b are desirably driven synchronously such that the peak amplitudeof vibration will occur approximately at the same time for bothactuators 506 a,b. The amplitude of vibration may differ between theactuators 506 a,b.

FIG. 35 shows a control embodiment in accordance with the presentdisclosure where the vibration device controller 502 includes aninternal direction and amplitude controller 508, an internal frequencycontroller 510, and an internal vibration controller 512. The directionand amplitude controller 508 desirably specifies the combined vibrationamplitude, Acombined, and the direction of vibration theta. Thefrequency controller 510 desirably specifies the vibration frequency, f.The vibration controller 512 uses the inputs of theta, Acombined, and fto output vibration commands to the individual actuators 506 a,b. Thevibration controller 512 is operable to output various waveformsincluding sine waves, square waves, triangle waves, or other profiles asdiscussed herein.

The output from the vibration device controller 502 shown in FIG. 35provides the magnitude of vibration as a function of time to each drivecircuit 504 a,b. In the case where the profile of vibration is a sinewave, the amplitude of vibration for each actuator as a function of timeis given by the equation shown below:

$\begin{matrix}{\begin{bmatrix}{A_{1}(t)} \\{A_{2}(t)}\end{bmatrix} = {D^{- 1}{{Acombined}\begin{bmatrix}{\cos({theta})} \\{\sin({theta})}\end{bmatrix}}{{\sin\left( {{\omega\; t} + p} \right)}.}}} & (28)\end{matrix}$Here, t is time and ω is the vibration frequency in radians per second.The parameter p is the phase of vibration and may be set to zero. Thevalue of ω in terms of frequency f in vibrations per second is given byω=2πf.

When the vibration actuators have a linear relationship between thecommand magnitude and the magnitude of vibration, the output A₁(t) andA₂(t) from equation 28 can be applied directly to the vibrationactuators to generate a combined vibration direction corresponding tothe angle theta. However some vibration actuators may have a nonlinearrelationship between the command magnitude and the magnitude ofvibration. For such nonlinear actuators it is possible to generatevibration in the direction theta by using a linearization function thatadjusts the magnitude of A₁ and A₂ to compensate for the nonlinearity ofthe actuator, as shown in the following equation.

$\begin{matrix}{\begin{bmatrix}{A_{1}(t)} \\{A_{2}(t)}\end{bmatrix} = {{linearziation\_ function}\left\{ {D^{- 1}{A_{combined}\begin{bmatrix}{\cos({theta})} \\{\sin({theta})}\end{bmatrix}}{\sin\left( {{\omega\; t} + p} \right)}} \right\}}} & (29)\end{matrix}$The linearization equation described above can be a lookup table or ascaling algorithm or other type of function.

The ability to control the direction of vibration over time, such asthough use of equations 28 and 29, is an important advantage of thepresent disclosure. The ability to control vibration direction can beused in vibratory feeders to direct parts in a desired direction. Inaddition, there are numerous advantages of using the disclosure forhaptic devices as described herein.

FIG. 36A illustrates a system 550 showing the input of various inputparameters of amplitude, phase and position (or time) for a pair oflinear actuators. A computer 552 receives input of the parameters, whichare preferably entered using a computer keyboard (not shown); however,the parameters also could be input using a graphical user interface,analog potentiometers, or many other means generally known to thoseskilled in the art. The appropriate output waveforms for linearactuators 554 a and 554 b are then computed using the computer 552. Eachwaveform is preferably independent. While computation may be performedusing an analog computer, a digital computer is preferred.

If a digital computer is used, the digital output for each actuator 554a,b is then preferably fed into respective digital-to-analog (“DAC”)converters 556 a and 556 b, which convert the output to the appropriateanalog waveform. The analog waveforms are then fed into the appropriatedriver circuits 558 a and 558 b. Those skilled in the art could useother means to modulate the linear vibrations of each actuator 554 a and554 b, for example via pulse width modulated (“PWM”). Varying theparameters produces an extremely broad range and rich set of hapticsensations for the end user.

In addition to creating varying force effects, one could control thedirection of vibration—that is to say the direction of vibration couldremain stationary. The resultant force effects can be of lower frequencythan the frequency of vibration.

There are also useful applications for generating precise patterns ofvibrations from simple parameters. Such patterns include circles,ellipses and straight lines. Furthermore, the amplitude and duration ofthe patterns may be precisely controlled over time. Moreover, a sequenceof patterns may be generated as desired.

FIG. 36B illustrates the system 550 where the input of various inputparameters includes input of pattern number, amplitude, duration andstart-time for the vibration device using compound vibrations. Theparameters are preferably entered using a computer keyboard. Theappropriate output waveforms for each linear actuator are then computedat computer 552. As described above, the digital output for eachactuator 554 a and 554 b is then fed into DACs 556 a and 556 b forconversion to the appropriate analog waveforms. The waveforms are thenfed into the driver circuits 558 a and 558 b. Again, the variousparameters produce an extremely broad and rich set of haptic sensationsfor the end user.

Each of the vibration devices described herein according to the presentdisclosure can be used as a haptic interface. Haptic interfaces provideforce sensation to a user. Haptic interfaces include computer gamingcontrollers, robot controllers, surgical tool controllers, as well asother devices where a force sensation is provided to a user.

An embodiment 600 of the present disclosure with a haptic interfaceapplication is shown in FIG. 37. In this embodiment a systems controller602 provides force commands to a haptic interface 604 which generatesforces which result in force sensations to user 606. The systemscontroller 602 may be microprocessor, a central processing unit, anASIC, a DSP, a game controller, an analog controller, or other type ofcontroller or any combination thereof. The user 606 can input commandsto the haptic interface 604 that are transmitted as user commands backto the system controller 602. The user commands can be input throughpressing buttons, moving joysticks, squeezing the haptic interface atvarious level forces, moving the haptic interface, applying force andtorque onto the haptic interface and through other means.

In the embodiment shown in FIG. 37, there is preferably a graphicaldisplay 608 which receives an image command from the system controller602 and displays a visual image to the user 606. The graphical display608 may be, for instance, a computer monitor, a television monitor, anLCD display, a plasma display, a combination of light sources, or othertype of means for generating a graphical image. A haptic interfaceapplication can also be implemented without a graphical display 608.

A haptic interface application can include a simulation of a virtualenvironment or representation of a real environment to the user 606. Asystems controller method of control can be based upon this real orvirtual environment. Typical simulated environments include games,driving and flight simulations, surgical simulations, and other types ofsimulations. Typical real world environments include control of robotsand remote machines, long distance interactions, and other types ofenvironments. It is often desirable that a haptic interface provideforce sensations that correlate with the real or simulated environmentin which the haptic interface is being used.

Another embodiment 620 having a haptic interface application is shown inFIG. 38. This embodiment is similar to the one of FIG. 37, and includesa systems controller 622, which provides force commands to a hapticinterface 624 that generates forces which result in force sensationsbeing received by user 626. A graphical display 628 is also provided forreceiving image commands from the system controller 622 and fordisplaying a visual image to the user 626.

In the embodiment of FIG. 38, the haptic interface 624 desirablyincludes a vibration device 630 having vibration actuators (not shown),a vibration controller 632, driver circuits 634 which drive thevibration device actuators, and an input device 636, which can detectuser input and which can include buttons, joysticks, and pressuresensors. The components of the haptic interface 624 may be of any of theconfigurations described herein. In this embodiment the graphicaldisplay 628 preferably presents a two dimensional image. The graphicaldisplay 628 shows an object of interest at a direction specified by theangle theta. It is may be desirable that the force sensation felt by theuser 626 correspond to the image on the graphical display in terms ofdirection, such as theta, and other attributes.

The embodiment shown in FIG. 38 can be utilized so that the forcesensations felt by the user 626 are generated by the vibration devicecontroller 632 specifically to correspond to the image on the graphicaldisplay 628. The vibration device controller 632 may specify one or moreof the amplitude of vibration, Acombined, direction of force, theta, andfrequency of vibration, f, as described above. The values of Acombined,theta, and/or f can be selected to correspond to the image on thegraphical display 628 and the environment being used by the systemcontroller 622. The complete force effect (including frequency,amplitude, combined direction of force and torque, and duration of forceeffect) generated by the vibration device may correlate events within agraphical computer simulation. Several examples of such operationfollow.

A first example involves the simulation of a user firing a gun. In thissimulation, the vibration device controller 632 could specify the angletheta to represent the direction of a gun firing, the amplitude ofvibration, Acombined, to represent the amplitude of the gun recoil, andthe frequency of vibration, f, to represent the frequency of bulletsleaving the gun.

A second example involves an impact between objects. In this simulationthe vibration device controller 632 may specify the angle theta torepresent the direction of impact, and the amplitude of vibration,Acombined, to represent the amplitude of impact.

A third example involves driving a vehicle. In this simulation thevibration device controller 632 could specify the angle theta torepresent the direction of vehicle motion, the frequency of vibration,f, to represent the frequency of vehicle vibration as it drives overbumps in the road or the speed of the vehicle, and the amplitude ofvibration, Acombined, to represent the amplitude of bumps in the road.

A fourth example involves a car or spacecraft spinning out of control.In this simulation the vibration device controller 632 could specify anangle theta that represents the vehicle's orientation. To represent thevehicle spinning, the angle theta can vary over time. The rate at whichthe angle theta can be different than the vibration frequency. Typicallythe frequency at which a vehicle spins would be significantly lower thantypical vibration frequencies.

An algorithm that can be used to create the vehicle spinning describedabove varies the direction of vibration continually. The direction ofvibration may be rotated at a rate of β radians per second, using theequation below:

$\begin{matrix}{\begin{bmatrix}{A_{1}(t)} \\{A_{2}(t)}\end{bmatrix} = {D^{- 1}{A_{combined}\begin{bmatrix}{\cos\left( {\beta\; t} \right)} \\{\sin\left( {\beta\; t} \right)}\end{bmatrix}}{\sin\left( {{\omega\; t} + p} \right)}}} & (30)\end{matrix}$

Equation 30 illustrates that the frequency of direction change, β, canbe modified independently from the frequency of vibration ω. A user suchas user 606 or 626 can sense both the frequency of vibration and thedirection of vibration. In this fashion, sensations at both the β and ωfrequencies can felt by the user. It is possible to set the frequency βmuch lower than the frequency ω, thereby overcoming a limitation ofknown devices. By way of example only, ω may vary between 10 Hz and 100Hz while β may be on the order of 1 Hz. In another instance, β may varyfrom between about 5% to 20% of ω. Of course, in other instances ω and βmay be similar or the same, or, alternatively, β may be larger than ω.All of these examples will depend on the specific effect that isdesired.

Low frequency operation is desirable in some situations, for instance ingames that have low frequency effects. For instance, games may generateactions or events in the sub-200 Hertz range, such as between 1 and 150Hertz. In certain cases the actions or events may be as low as 2 Hertzor lower, such as about 0.5-1 Hertz. Examples of such actions/eventsinclude gunshots, automobile related sounds such as corresponding to acar spinning out of control, and helicopter related sounds such as thewhirring of the rotor blades. A traditional eccentric mass actuator maynot be suitable to generate a haptic sensation in this frequency range;however, two or more vibration actuators operated in synchronizedvibration may generate such frequencies.

β is not limited to any particular rate or range of rates. For instance,β may be a relatively low rate to represent a slow spinning action,e.g., of a car spin out at less than 10 miles per hour, or β may be arelatively high rate to represent a fast spinning action, e.g., of a carspin out at a speed in excess of 40 miles per hour. Similarly, ω is notlimited to any particular frequency of vibration. Preferably, ω is setwithin a range of frequencies that can be felt or otherwise detected bya user.

Equation 30 may be modified by changing the vibration profile from asine wave to a square wave, triangle wave, or other profile. Inaddition, the amplitude of vibration, Acombined, can be varied overtime. The frequencies β and ω can also be varied over time. In thisfashion a wide range of force effects can be created.

Vibration actuators can be used to provide haptic sensations eitherthrough synchronized vibration or otherwise. Actuators can be vibratedwithout synchronization when there is no need to convey directionalinformation, and then the actuators can be switched to synchronousvibration when there is a need to convey directional information thoughthe haptic interface.

Many linear motion vibration actuators take advantage of resonance toachieve relatively high level of forces with low power requirements.However, to achieve these high levels of forces a number of vibrationcycles have to occur before the peak magnitude of vibration occurs. Inaddition when the actuator is shut off, the moving mass in the actuatormay continue to oscillate for a number of cycles. Thus the dynamics ofthe actuator prevents instantaneous response of the actuator to increaseor decrease the magnitude of vibration.

When synchronous vibration is used to control the direction of combinedforce, the actuator dynamics may limit the speed at which the directionof combined force can be changed. One of the examples presented abovedescribes implementation of a haptic force sensation that corresponds tothe spinning of a car. However, the actuator dynamics may limit the rateat which such spinning effect can be generated. As will be described indetail below, it is possible to provide a method that can increase therate at which the direction of force can be changed for a system ofvibration actuators that are synchronously vibrated.

Equation 25 above defines the required amplitude of vibration ofactuators to achieve a combined force direction corresponding to anangle theta. For a given actuator in a vibration device, the requiredamplitude of vibration is defined as Ades, which indicates the desiredamplitude of vibration of that actuator. If the actuator is at rest orat a lower level of vibration than Ades, then it may be desirable toinitially drive the actuator at a higher level of vibration to morequickly raise the amplitude of vibration to Ades. Conversely if theactuator is already vibrating at an amplitude higher than Ades it may bedesirable to initially drive the actuator at a lower level or even brakethe actuator to more quickly lower the amplitude of vibration to Ades.These variations in the amplitude at which the actuator is driven aredefined as corrections to the commanded vibration magnitude.

One method of determining the proper corrections to the vibrationmagnitude is to model the dynamics of the actuator. This approach allowsone to predict the dynamic states of the actuator and optimal commandsto most quickly generate the desired amplitude of vibration.

An alternate method of determining the corrections to the vibrationmagnitude does not require a dynamic model of the actuator or explicitlypredicting the dynamic states of the actuator. In this method a counteris maintained to track the recent number of vibrations of the actuatorand the corresponding commands sent to the actuator during these recentvibrations. The command to the actuator at the k^(th) vibration is givenby the following equation:A _(com) _(—) _(k) =A _(des) _(—) _(k) +A _(cor) _(—) _(k)

A_(des) _(—) _(k) represents the desired actuator amplitude for thek^(th) vibration of the actuator. A_(cor) _(—) _(k) represents thecorrection to the command for the k^(th) vibration. And A_(com) _(—)_(k) represents the actual amplitude of the command sent to the actuatorfor the k^(th) vibration.

If the desired amplitude at the k^(th) vibration is greater than theamplitude during the previous vibration, then most likely the vibrationlevel needs to be increased. Accordingly, the correction to the commandat vibration k, A_(cor) _(—) _(k), can be chosen to be proportional tothe difference between the current desired amplitude, A_(des) _(—) _(k),and the previous commanded amplitude A_(com) _(—) _(k-1). An equationwhich described this approach for calculation A_(cor) _(—) _(k) is:A _(cor) _(—) _(k) =K*(A _(des) _(—) _(k) −A _(com) _(—) _(k-1))  (31)

Here, K is a gain chosen based upon actuator performance. This sameequation works for reducing the magnitude of vibration quickly. WhenA_(des) _(—) _(k) is less than the value of A_(com) _(—) _(k-1), itindicates that most likely the level of vibration needs to be reducedand the correction A_(cor) _(—) _(k) is negative. If the large reductionin vibration amplitude is commanded, then the negative magnitude ofA_(cor) _(—) _(k) may be greater than A_(des) _(—) _(k) and the actualcommand sent to the actuator, A_(com) _(—) _(k), will be negativeresulting in braking of the moving mass in the actuator.

Another approach to correcting the magnitude of vibration takes intoconsideration the two previous commanded amplitudes, and is given by thefollowing equation:A _(cor) _(—) _(k) =K ₁*(A _(des) _(—) _(k) −A _(com) _(—) _(k-1))+K₂*(A _(des) _(—) _(k) −Acom_(k-2))  (32)

Here K₁ is a gain that corresponds to the k−1 vibration command, and K₂is a gain that corresponds to the k−2 vibration command. In a similarfashion even more prior commands can be incorporated into the correctionalgorithm. The following equation shows how “m” prior commands can beincorporated into an actuator command.A _(cor) _(—) _(k) =K ₁*(A _(des) _(—) _(k) −A _(com) _(—k-1) )+K ₂*(A_(des) _(—) _(k) −A _(com) _(—) _(k-2))+ . . . +K _(m)*(A _(des) _(—)_(k) −A _(com) _(—) _(k-m))  (33)

Alternative methods of control for multiple vibrating actuators mayinclude modified synchronization. One method of modified synchronizationis for one actuator to vibrate at a frequency that is an integermultiple of the vibration frequency of another actuator. FIG. 39 is aplot 650 presenting two vibration profiles, 652 and 654, showing such acontrol method. The vibration frequency of profile 654 is twice thevibration frequency of profile 652. The beginning of cycles of vibrationcan be controlled to occur at the same time only ever other cycle forprofile 2. Thus the superposition of, peak amplitudes only occurs everother cycle for profile 654. This modified synchronization method can beapplied for arbitrary integer multiples of vibration frequency,arbitrary vibration profiles, and an arbitrary number of actuators.

One advantage of such a modified synchronization method is that multiplevibration frequencies can occur at the same time while still providingfor some superposition or peak amplitudes. The superposition of peakamplitudes allows for control of direction of vibration, in a similarfashion to how the direction for vibration is controlled forsynchronized, vibration. With this modified method of synchronizedvibration, it is possible to specify the direction of combined forceonly during a portion of the vibration cycle. Nevertheless, a directioncomponent to the vibration can be controlled in the duration close tothe time where the superposition of peaks occurs. Close to the time atwhich there is superposition of peaks in the vibrations, the combinedforce vector, F_(combined), can be approximated by:F _(combined) =a ₁ A ₁ +a ₂ A ₂  (34)

Here, a₁ and a₂ are the unit vectors aligned with the directions ofactuator 1 and actuator 2, respectively. A₁ and A₂ are the amplitudes offorce of actuator 1 and actuator 2, respectively, near the duration ofthe superposition of peaks. By modifying the amplitudes A₁ and A₂ it ispossible to modify the amplitude and direction of the combined forcevector, F_(combined). A similar approach can be used when there are morethan two vibration actuators.

If there are two or more vibrating actuators where repeatedly the peakamplitude of force of these vibrating actuators occurs at approximatelythe same time, then the combined direction of force of these actuatorscan be controlled near the time when these repeated peak amplitudesoccur. In this case, the combined direction of force can be controlledby modifying the amplitude of vibration of the actuators.

An alternative modified synchronization is to drive two vibrationactuators at the same frequency but one vibration actuator at a phasewhere its peak magnitude of force occurs when a second vibrationactuator is at zero force, which is at 90 degrees out of phase for asinusoidal vibration. In such a modified synchronization the combinedforce direction rotates in a circle or ellipsoid during each vibrationperiod.

Additional methods for modified synchronization of vibration may includethe superposition of profiles as described in the “Jules Lissajous andHis Figures” (“Lissajous”), appearing in chapter 12 of “TrigonometricDelights” by Eli Maor, published in 1998 by Princeton University Press.The entire disclosure of Lissajous is hereby incorporated by reference.Lissajous describes how profiles can be combined through variouscombinations of frequencies, phases, amplitudes, and profiles togenerate a wide range of output figures. These are also known asBowditch curves. Lissajous also describes how geometric shapes can becreated from multiple vibration sources. These combinations ofvibrations can be applied to haptic devices and vibration devices inaccordance with aspects of the present disclosure. Thus, the concepts ofsuperposition described in Lissajous can be applied by vibrationactuators to yield a wide range of force sensations.

Electric actuators often require a driver circuit separate from acontroller. The driver circuit provides sufficient current and voltageto drive the Actuators with the necessary electrical power. A wide rangeof driver circuits have been developed for electrical actuators andspecifically for vibration actuators, and are known to those skilled inthe field. Such driver circuits include linear drivers, PWM drivers,unipolar drivers, and bipolar drivers. A circuit block diagram for avibration actuator 700 according to the present disclosure includes avibration controller 702, a driver circuit 704, and an actuator 706, asshown in FIG. 40.

The vibration controller 702 shown in FIG. 40 can be located on thevibration device itself or could be located remotely, where thevibration signals are transmitted to the driver circuit 704 throughwired or wireless communication.

It is often desirable to control a vibration device or actuators from adigital controller such as a microprocessor or other digital circuit.Digital control circuits often have low level power output, andtherefore require a higher power driver circuit to drive an actuator. Inaddition, low cost digital controllers often have digital outputs, butdo not have analog outputs. To simplify the vibration controllercircuitry and lower cost, the vibration signal can be a binary logicdirectional signal which signals the moving mass to move either forwardor backwards. In this configuration, the vibration signal can be in theform of a square wave to generate the desired vibration effect. Evenwith such a square wave control signal, the actual motion and vibrationforce of the vibration actuator will most likely not follow a squarewave exactly due to the dynamics of the actuator.

To further simplify the vibration controller circuitry and lower cost,the amplitude of the vibration signal can be modulated with a PWMsignal, where the duty cycle of the signal is proportional to theamplitude of vibration. An embodiment 710 with such a digital vibrationcontroller 712 for one actuator 716 is shown in FIG. 41. In thisembodiment, the output of the digital vibration controller 712 includesan amplitude signal in PWM form and a direction signal, for instance inthe form of a logic bit, both of which preferably are sent to a drivercircuit 714. The driver circuit 714, in turn, sends electrical power tothe actuator 716.

Digital control circuitry can be used to control a complete vibrationdevice in synchronized vibration. In synchronized vibration thefrequency and phase of two or more actuators are the same. Accordingly,a single square wave can be used to control the direction of thevibration actuators that are in synchronized vibration. The amplitude ofvibration can be controlled independently for each actuator, withseparate PWM signals.

FIG. 42 shows an embodiment 720 where a vibration device controller 722generates one directional signal (“dir”), which may be in the form of asquare wave. The dir signal is preferably provided to a pair of drivecircuits 724 a and 724 b. The vibration device controller 722 desirablygenerates separate amplitude signals, A1 and A2, in PWM form to thedrive circuits 724 a,b for a pair of actuators 726 a and 726 b. Thevibration device controller 722 preferably includes a direction andamplitude controller 728, a frequency controller 730 and a vibrationcontroller 732 as in the embodiment described above with regard to FIG.35. The direction and amplitude controller 728, the frequency controller730 and the vibration controller 732 may be configured in hardware,software, firmware or a combination thereof, and may be implementedeither as separate components or processes, or may be implemented as asingle component or process.

The embodiment 720 of FIG. 42 may be used to control in synchronousvibration the vibration devices with two actuators, for instance asdescribed above with regard to FIGS. 10-20. Embodiment 720 can also beused to vibrate two or more actuators completely out of phase, whichoccurs during synchronized vibration when equation 25 provides resultswith the sign of A1 being different than the sign of A2. To vibrate twoactuators completely out of phase, the binary direction signal dir canbe inverted for one of the actuators. The inversion of the directionalsignal dir can occur at a driver circuit 724 a or 724 b, or thevibration controller 732 can output two directional signals, with onebeing the inverse of the other. The case where two actuators are beingdriven completely out of phase is shown in FIG. 13.

Electric actuators in accordance with the present disclosure can bedriven with unipolar or bipolar drivers. A unipolar driver will generatecurrent in an actuator in a single direction. A unipolar driver is wellsuited for actuators where the moving mass is ferromagnetic and anelectromagnetic coil only generates attractive magnetic forces, such asthe actuator 150 shown in FIG. 9. One example of a unipolar drivercircuit is a Darlington array, such as the ULN2803A DARLINGTONTRANSISTOR ARRAY manufactured by Texas Instruments.

A bipolar driver can generate current in two directions. Bipolar driversare well suited for actuators where the moving mass is magnetic andwhere reversing the direction of current in an electromagnetic coil canreverse the direction of force on the moving mass. Examples of suchactuators are presented in FIGS. 5A-B through 8A-B. One example for abipolar driver circuit is an H bridge, such as the L298 manufactured byST Microelectronics. Alternative H bridges are the 3958 and 3959 driversmanufactured by Allegro Microsystems.

In vibrating circuits it can be advantageous to increase power output ofthe driver circuits through use of a charge pump capacitor as used in3958 and 3959 drivers manufactured by Allegro Microsystems. It can alsobe advantageous to incorporate a capacitor in series with a linearmotion vibrating actuator to benefit from a resonance effect andtemporary storage of energy in the capacitor, as described in theaforementioned U.S. patent application entitled “Vibration Device.”

As detailed herein, vibration actuators can be used in a variety ofmethods to create haptic effects. Vibration actuators can be operatedcontinuously throughout the duration of a specified haptic effect, orcan be pulsed on and, off during the haptic effect. By pulsing vibrationactuators on and off the user feels only a small number of vibrations,then feels a pause, and then the vibration resumes. In this fashion itis possible to generate secondary sensations associated with thefrequency of pulsing the actuators on and off. Examples of how suchpulse effects can be used are described in U.S. Pat. Nos. 6,275,213 and6,424,333.

Any of the actuators described herein may be used in accordance with thepresent disclosure to produce a wide variety of haptic effects. Whilesome actuators such as linear actuators and rocking mass actuators maybe particularly suited for low frequency operation, all actuators hereinmay provide synchronized feedback. Such feedback may be employed ingames, virtual reality equipment, real-world equipment such as surgicaltools and construction equipment, as well as portable electronic devicessuch as cellular phones and pagers. By way of example only, cellularphones and pagers may implement different vibration effects to identifydifferent callers or different actions. Synchronized vibration mayprovide directional feedback, for instance, with the impact or recoil ofa gun in a game, or to distinguish between frontal and side impacts indriving games. Synchronized vibration may also provide a continualrotation of a vibration force vector in a game to simulate a carspinning out of control. Synchronized vibration may also be used inendless other applications and situations to provide a rich hapticexperience to a user.

As mentioned above, other aspects of the disclosure include GeneralSynchronized Vibration. General Synchronized Vibration differs fromnon-synchronized vibration in that the frequency and phase of multiplevibration forces are controlled. Embodiments with multiple VibrationActuators that are not controlled with the General SynchronizedVibration approach will often have inconsistent frequency, amplitude, orrelative phase between the actuators. With General SynchronizedVibration the frequency and phase of the Vibration Actuators may varyduring the start-up and transitions between various waveforms. However,once the actuators are synchronized, each actuator is controlled to aspecific frequency and phase.

Often each actuator is controlled to a fixed frequency and phase for agiven duration of time. This duration of time depends on theapplication, but is typically longer than the period of the highestfrequency vibration force that is being synchronized. In hapticapplications this duration of time is typically along enough for aperson to sense the effect. However, there are some implementations ofGeneral Synchronized Vibration where the desired waveform of vibrationvaries quickly, such as a quickly changing direction used to provide asensation of spinning. In such quickly varying waveforms, the desiredfrequency and phase of a vibration actuator may be changing in aduration that is shorter than the period of the vibration of thatactuator. A common characteristic of General Synchronized Vibration isthat the frequency and relative phase of multiple vibration actuatorsare explicitly controlled to desired values rather than randomlyselected values.

In General Synchronized Vibration there is typically a consistentcorrelation between frequency and phase of the actuators and desiredvibration effects. For example, a haptics effect library for softwaredevelopers may have a routine labeled “spin,” which generates a sequenceof desired frequency and phase for a plurality of Vibration Actuators.Each time the spin effect is executed, a similar sequence of frequencyand phase and generated by the plurality of Vibration Actuators.

Embodiments of this disclosure include a Vibration Device comprised ofmultiple Vibration Actuators mounted onto a mounting platform such as abase plate, sub-frame, housing, or enclosure. For example the mountingplatform could be the housing of a game controller, or the housing of aVibration Actuator. The mounting platform transfers force and torquebetween the Vibration Actuators and thereby allows the vibration forcesand torques to be superimposed upon each other. The mounting platform ispreferably rigid, but can also be relatively rigid component, or asemi-rigid component. The mounting platform could be made of separatepieces. The mounting platform could include components of an object uponwhich vibration forces are being applied. For example if multipleVibration Actuators are mounted onto a person's arm or other body partsand forces are transmitted from these actuators through the arm or bodyparts, then the arm or body parts can serve as the mounting platform.This disclosure pertains to any configuration where the forces andtorques from multiple Vibration Actuators can be vectorially combined togenerate a net vibration force, vibration torque, or vibration force andtorque.

The mounting platform is typically attached to a number of items such asbattery, control circuit board, and the stationary parts of theVibration Actuators including housing and stator. The combined mass ofthe mounting platform and items that are attached to it is defined as a“Reference Mass”. The vibration force and torques are transferred fromVibration Actuators to the Reference Mass. If the mounting platform isable to move, the vibration forces may shake the Reference Mass.Typically the Reference Mass is in contact with an “External Object”,and forces and torques are transmitted between the Reference Mass andthe External Object. For example, a game controller held in a user'shand would transfer forces and torques from the game controller'sReference Mass onto a user's hands, which in this case is an ExternalObject. The mounting platform may be attached to the Earth, which wouldalso be an External Object. A Vibration Device attached to the Earth issometimes termed a “Shaker” or a “Shaker Device”.

A preferred embodiment uses two aligned LRAs, as shown in FIG. 43. LRA1102 a and LRA 1102 b are attached to mounting platform 1100 and arealigned in the axis of vibration that they generate. Each LRA has amoving mass, 1108, and a housing 1106 which is attached to the Mountingplatform 1100. This configuration of vibration actuators is referred toas an LRA Pair. The vibration forces from each LRA are combined togetherthrough the mounting platform 1100. The vibration force generated by LRA102 a is designated as F1 and the vibration force generated by LRA 1102b is designated by F2.

For the embodiment shown in FIG. 43, one method of generating anasymmetric vibration force is to operate LRA 1102 b at twice thefrequency of LRA 1102 a, with a specified phase difference of either 90or −90 degrees. The vibration forces in such an embodiment withsinusoidal vibrations can be given by:F ₁ =B ₁ sin(ω₁ t+φ ₁)F ₂ =B ₂ sin(ω₂ t+φ ₂)

-   -   Where ω₂=2ω₁    -   φ₁=0, and φ₂=−90

The combined force for the LRA Pair is given by:F _(LRA) _(—) _(Pair) =B ₁ sin(ω₁ t+φ ₁)+B ₂ sin(ω₂ t+φ ₂)  (35)

Typically it is not critical to control vibration effects relative toabsolute time. Accordingly, when implementing the vibration effectdescribed in Eq. 35 above, it is not critical to control both the phaseφ₁ and φ₂, but rather the relative phase between the two actuators.Therefore in some implementations one could set phase φ₁ to zero andcontrol only φ₂. Alternatively one could directly control the phasedifference between the actuators. In this application typically thephases of all the actuators are shown in the equations. However, withoutloss of utility only the relative phase of the actuators can becontrolled. Thus the phase of Vibration Actuators 2, 3, 4, etc. would becontrolled relative to the phase of actuator 1; thereby eliminating theneed to control the phase of actuator 1 relative to absolute time.

A feature of this disclosure includes the use of superposition ofsynchronized vibration waveforms. When multiple vibration forces aregenerated on a single vibration device, the Combined Vibration Force forthe device is the superposition of the multiple waveforms. An examplewith two synchronized sine waves described by Eq. 35 is shown in FIG.44. As shown, waveform 2 has twice the frequency of waveform 1. Thephase of both waveforms is set such that at a time of zero the peaks ofboth waveforms have their maximum value in a positive direction, and theforces magnitudes are added together (also referred to as constructiveinterference or positive interference).

Furthermore, at the time when waveform 1 is at its negative peak thenwaveform 2 is at a positive peak, and the forces magnitudes aresubtracted from each other (also referred to as destructive interferenceor negative interference). Due to this synchronization the combinedvibration waveform is asymmetric, meaning that the force profile forpositive force values is different than the force profile for negativeforce values. In the asymmetric waveform shown in FIG. 44 there is ahigher peak positive force and a lower peak negative force. In hapticapplications the larger force in the positive direction can generatemore of a force sensation than the lower magnitude force in the negativedirection, even though the duration of force in the negative directionis longer. In this fashion asymmetric vibrations can be used to generatea haptic cue in a specific direction with a vibration device.

In an LRA, a moving mass moves relative to the actuator housing, and arestoring spring transfers force between the moving mass and theactuator housing. The force imparted by an LRA onto a mounting platformis a combination of the force from the restoring spring, and theelectromagnetic force between the stator and moving mass. The restoringspring can be, for example: a mechanical spring or a magnetic spring. Asresonance builds up in an LRA, the magnitude of the spring restoringforce increases and becomes the dominant portion of the actuator force.Accordingly, the peak force imparted by a LRA onto the mounting platformtypically occurs at or near the peak excursion point of the moving mass.

In FIG. 43 the moving masses are graphically depicted as towards theright side of the LRAs to indicate actuator forces being applied to theright. Accordingly, when the embodiment shown in FIG. 43 is controlledto follow the waveform described by Eq. 35, then the moving mass of LRA1102 a is at its peak excursion to the right at the same time when themoving mass of LRA 1102 b is at its peak excursion to the rightresulting in a large combined force to the right, yet when the movingmass of LRA 1102 a is at or near its peak excursion to the left then themoving mass of LRA 1102 b is at or near its peak excursion to the right(since it is vibrating at twice the frequency) resulting in forcecancellation and a low combined force to the left.

Thus, in this embodiment the timing of the moving masses is anindication of an asymmetric vibration waveform. In FIG. 45, theembodiment shown in FIG. 43 is shown at various time steps as itimplements the vibration waveform shown in FIG. 44. In 45, the top LRAvibrates at twice the frequency and generates lower forces that thebottom LRA, the position of the moving masses indicates the forcesgenerated by each LRA, and the combined force vector is shown betweenthe LRAs. Each time step in FIG. 45 is labeled according to the period,T, of the slower LRA.

In the embodiment shown in FIG. 43, the alignment of the actuators doesnot have to be precise. Indeed, in haptic applications having the twoactuators are not precisely aligned may not deter from the primaryhaptic effect that is being generated.

A variation of this embodiment is shown in FIG. 46. The actuators 1102 aand 1102 b are attached directly to each other to provide an even morecompact configuration. Also the LRAs can share housings, shafts, powersupplies, and other components to make the device even more compact.

Another variation of this embodiment is shown in FIG. 47. The actuators1102 a and 1102 b are attached in line with each other. In thisembodiment, the forces of each LRA are collinear, and create no nettorque along the axis of the LRAs. This embodiment is useful where pureforce output is desired without any torque output.

The timing of vibration force within a Vibration Actuator can becorrelated with a number of physical properties. For example, in manyLRAs a spring applies a restoring force onto a moving mass and thevibration force is largely correlated with the position of the movingmass. In ERMs the direction of the vibration force largely correlates tothe angular position of a rotating eccentric mass. Linkage mechanismscan be used to generate vibrations, such as a slider-crank vibrationactuator 1110 shown in FIG. 48, where a rotating motor 1114 moves a mass1120 back and forth. With such linkages the vibration force can becorrelated with the acceleration of a moving mass. Since the vibrationforce can be correlated with a number of physical properties, GeneralSynchronized Vibration can also be characterized by control of thefrequency and phase of the position or acceleration of moving masseswithin Vibration Actuators.

A feature of this disclosure includes combining vibration waveforms frommultiple Vibration Actuators to generate a more complex vibrationwaveform. The asymmetric vibration described by Eq. 35 and shown in FIG.44 is only one such type of combined vibration waveform. A more generalembodiment shown FIG. 49 has a set of N LRAs all aligned with the sameaxis. According to one aspect, in General Synchronized Vibration aplurality of Vibration Actuators are synchronized in phase andfrequency, and in some cases amplitude. A wide range of vibrationeffects can be generated by controlling the frequencies and phases ofall N actuators.

A vibration force, F, is in a repeated cycle over a period T whenF(t+T)=F(t). The vibration force of an ith actuator in a repeated cyclecan be given by:F _(i)(t+Δ _(i) +T _(i))=F _(i)(Δ_(i) +t),where Δ_(i) is the phase and T_(i) is the period of the ith actuator.For the embodiment shown in FIG. 49, there is a set of N LRAs allaligned with the same axis. If all actuators are operated at setfrequencies and phases, then the combined vibration force can be givenby:F _(AlignedSet) =F ₁(Δ₁ +t)+F ₂(Δ₂ +t)+ . . . +F _(N)(Δ_(N) +t)  (36)

In the general case, the waveform shapes of F_(i) can be a wide range ofwaveforms including sine waves, triangle waves, square waves, or otherwaveforms. In some embodiments, the frequency of the actuator with thelowest frequency is defined as the fundamental frequency, ω₁, and theremaining actuators vibrate at integer multiples of the fundamentalfrequency. In these embodiments the period of the fundamental frequencyis given by T₁ and the remaining vibration periods are given by suchthat:T ₁=2T ₂ ,T ₁=3T ₃ , . . . T ₁ =NT _(N)

When all the vibration actuators vibrate at integer multiples of thefundamental frequency, then the combined waveform has a repeatedwaveform with a period of the fundamental frequency. The fundamentalfrequency is also referred to as the first harmonic.

One method of implementing General Synchronized Vibration is to usesinusoidal vibrations in each actuator of an aligned set, and useFourier Waveform Synthesis to select the phase, frequency, and amplitudeof each actuator to approximate a desired vibration waveform. For a setof N aligned actuators with sinusoidal waveforms, the combined force ofan Aligned Set, F_(AlignedSetFourier), is given by:F _(AlignedSetFourier) =B ₁ sin(ω₁ t+φ ₁)+B ₂ sin(ω₂ t+φ ₂)+ . . . +B_(N) sin(ω_(N) t+φ _(N))  (37)

A wide range of additional waveforms can be synthesized from a set (aplurality) of vibration waveforms. Fourier synthesis is a method wherebyan arbitrary waveform can be approximated from a combination of sinewaves, including both symmetric and asymmetric waveforms. It isadvantageous to use actuators vibrating at frequencies that are integermultiples of the frequency of vibration of other actuators. The lowestfrequency in the set is referred to as the fundamental frequency or thefirst harmonic, the second harmonic is twice the fundamental frequency,the third harmonic is three times the fundamental frequency, and so on.

An advantage of using harmonics is that all the waveforms in the setrepeat at the period of the fundamental frequency, thereby providing arepeating waveform profile of the combined waveform. In many vibrationapplications each vibration actuator generates a force with a repeatedwaveform that has a zero DC component and the combined force isdescribed by Eq. 37. Accordingly, the combined vibration force does nothave a DC component. Fourier synthesis is widely used in create a widerange of waveforms. One example waveform is a Sawtooth waveform, whichcreates a sudden change of force in one direction. In this manner, theSawtooth waveform can be used to generate directional haptic cues. Whenthe set of waveforms consists of three sine waves, the Sawtooth waveformcan be generated with the first harmonic at relative amplitude 1, thesecond harmonic is at relative amplitude of ½, and the third linear sinewave with a relative amplitude of ⅓. With Fourier waveform synthesis,arbitrary waveforms can be approximated including both symmetric andasymmetric waveforms. When using Fourier waveform synthesis, bothconstructive and destructive interference can occur for both thepositive and negative forces amplitudes.

An operating advantage of an LRA is to use resonance to generate highmagnitude vibration forces from a relatively low power input, and an LRAcan be designed and manufactured to have a specific resonant frequencyby optimizing its spring stiffness and moving mass. In embodiments ofGeneral Synchronized Vibration, it can be advantageous to select a setof LRAs with resonant frequencies that correspond to at least some ofthe harmonics of a desired waveform. For example for a vibration devicesuch as that in FIG. 49 with a set of n LRAs, the first LRA 1102 a couldhave a specified resonant frequency of ω₁, the second LRA 1102 b couldhave a specified resonant frequency of 2ω₁, the third LRA could have aspecified resonant frequency of 3ω₁, and so on through the nth LRA 1102n.

Although LRAs are generally designed to operate at their resonantfrequency, one can operate LRAs at other frequencies with loweramplitude force output per input command signal. Since lower amplitudeforce output is typically required at higher harmonics, once could builda Vibration Device with LRAs that all have the same resonant frequency,but operate them at different frequencies. For example for a vibrationdevice with a set of 2 LRAs, both LRAs could have a specified resonantfrequency of (3/2)ω₁, where the first LRA is driven at ω₁, and thesecond LRA is driven at 2ω₁. In this configuration both LRAs areamplifying the input signal, but less than if they were driven at theresonant frequency of the LRAs, which is (3/2)ω₁ for this example.

Asymmetric Vibration waveforms are useful for generating directionalhaptic cues, and can be synthesized using Fourier synthesis. Forinstance, an example of a method for selecting frequency, phase, andamplitude of sinusoidal vibrations to generate a high level of asymmetryis discussed below. Vibration parameters are specified for a set of 2,3, and 4 actuators. In addition a process is presented for identifyingparameters for waveforms with a high level of vibration asymmetry forany number of actuators. It should be noted that high levels ofasymmetry may be achieved even if the values specified by this exampleare only approximately implemented. For instance, in the case ofsuperposition of two sine waves, if there is a 30% error in theamplitude of vibration then 90% of desired asymmetry effect will stillbe realized.

Fourier synthesis allows one to approximate an arbitrary waveform with asuperposition of sinusoidal waves. However, it is advantageous in someapplications to generate asymmetric waveforms that have higher peakmagnitudes in the positive direction than in the negative direction (orvice versa). The question then becomes what is the best function toapproximate that will maximize the amount of asymmetry for a givennumber of superimposed sine waves? It is of special interest to considerasymmetric waveforms that have a zero DC component and thus can becomposed solely of sine waves. Waveforms with a zero DC component can beused to generate vibrations from a set of vibrators since each vibratorwill typically have a zero DC component. An asymmetric pulse train isillustrated in FIG. 50. The pulse-train is just one example of anasymmetric waveform, but it is a useful example. For the pulse-train tohave a zero DC component, the area above the axis. Thus:

W ⋅ P = (T − W)V, and ${V = \frac{W \cdot P}{\left( {T - W} \right)}},$where W is the pulse width, V is valley amplitude, T is period ofrepeated pulse, and P is peak amplitude.

The amount of asymmetry in a pulse-train can be defined by thepercentage increase of P over V. One could increase the amount ofasymmetry by reducing W, which would generate a thin and high pulse.However, if W is too small, the waveform would not be well-approximatedwith a small number of sine waves. Accordingly, an analytical questionis, “What is the optimal value of W for a waveform composed of N sinewaves?”

FIG. 51 illustrates a pulse-train with zero DC component. Given thiswaveform, one may find its Fourier coefficients according to the Fourierseries:

${{f(t)} = {a_{0} + {\sum\limits_{n = 1}^{N}\left( {{a_{n}{\sin\left( {2\pi\; n\; t} \right)}} + {b_{n}\;{\cos\left( {2\pi\; n\; t} \right)}}} \right)}}},$where f(t) is an arbitrary waveform and when a₀=0 it have zero DCcomponent. The Fourier coefficients can be calculated by multiplyingboth sides of the above equation by sin(2 π n t) or cos(2 π n t) andthen canceling out terms. The coefficients are:

$\frac{a_{n}}{2} = {\int_{0}^{T}{{f(t)}{\sin\left( {2\pi\; n\; t} \right)}{\mathbb{d}t}}}$$\frac{b_{n}}{2} = {\int_{0}^{T}{{f(t)}{\cos\left( {2\pi\; n\; t} \right)}{\mathbb{d}t}}}$a₀ = ∫₀^(T)f(t)𝕕t = 0

The equation for a₀ holds if the DC component is zero. For the pulsewaveform above, a_(n) is given by:

$\begin{matrix}{\frac{a_{n}}{2} = {{\int_{0}^{W}{P\;{\sin\left( {2\pi\; n\; t} \right)}{\mathbb{d}t}}} + {\int_{W}^{T}{\left( {- V} \right){\sin\left( {2\pi\; n\; t} \right)}{\mathbb{d}t}}}}} \\\left. {\left. {= \frac{{- P}\;{\cos\left( {2\pi\; n\; t} \right)}}{2\pi\; n}} \right\rbrack_{0}^{W} + \frac{V\;{\cos\left( {2\pi\; n\; t} \right)}}{2\pi\; n}} \right\rbrack_{W}^{T}\end{matrix}$$\frac{a_{n}}{2} = {\frac{{- P}\;{\cos\left( {2\pi\; n\; W} \right)}}{2\pi\; n} + \frac{P}{2\pi\; n} + \frac{V\;{\cos\left( {2\pi\; n\; T} \right)}}{2\pi\; n} - \frac{V\;{\cos\left( {2\pi\; n\; W} \right)}}{2\pi\; n}}$$\frac{a_{n}}{2} = {\left( \frac{1}{2\pi\; n} \right){\left( {P + {V\;{\cos\left( {2\pi\;{nT}} \right)}} - {\left( {P + V} \right){\cos\left( {2\pi\;{nW}} \right)}}} \right).}}$

In a similar fashion:

$\frac{b_{n}}{2} = {{\int_{0}^{W}{P\;{\cos\left( {2\pi\; n\; t} \right)}{\mathbb{d}t}}} + {\int_{W}^{T}{\left( {- V} \right){\cos\left( {2\pi\; n\; t} \right)}{\mathbb{d}t}}}}$$\frac{b_{n}}{2} = {\left( \frac{1}{2\pi\; n} \right)\left( {{\left( {P + V} \right){\sin\left( {2\pi\; n\; W} \right)}} - {V\;{\sin\left( {2\pi\;{nT}} \right)}}} \right)}$

By substituting in v from the equation above, the result is:

$\frac{a_{n}}{2} = \frac{{{- {PT}}\;{\cos\left( {2\pi\; n\; W} \right)}} + {{PW}\;{\cos\left( {2\pi\; n\; T} \right)}} + {PT} - {PW}}{{2\pi\;{nT}} - {2\pi\;{nW}}}$$\frac{b_{n}}{2} = {- \frac{{{PW}\;\sin\left( {2\pi\; n\; T} \right)} - {{PT}\;{\sin\left( {2\pi\; n\; W} \right)}}}{{2\pi\;{nT}} - {2\pi\;{nW}}}}$

FIG. 52 is a flow diagram illustrating a process for maximizingasymmetry. As shown in the flow diagram, the process includes selectinga number of sine waves, and then guessing (estimating) values for W.Fourier coefficients are then calculated, and the time domain of thewave, f(t), is generated according to the equation set forth above. Theamount of asymmetry in f(t) is then calculated. The process may berepeated with different values for W, and the value for W is selectedthat gives the most asymmetry.

Fourier coefficients can be represented by a_(n) and b_(n) as:

${f(t)} = {a_{0} + {\sum\limits_{n = 1}^{N}\left( {{a_{n}{\sin\left( {2\pi\; n\; t} \right)}} + {b_{n}{\cos\left( {2\pi\; n\; t} \right)}}} \right)}}$

An alternative representation using sine waves and phase is:

${f(t)} = {A_{0} + {\sum\limits_{n = 1}^{N}{A_{n}{\sin\left( {{2\pi\; n\; t} + \phi_{n}} \right)}}}}$

To relate the two representations, the addition of sines formula:sin(α+β)=sin(α)cos(β)+cos(α)sin(β)may be used with:α=2πntβ=φ_(n)A _(n) sin(2πnt+φ _(n))=A _(n) cos(φ_(n))·sin(2πnt)+A _(n)sin(φ_(n))cos(2πnt)

Let

$a_{n} = {{A_{n}{\cos\left( \phi_{n} \right)}\mspace{14mu}{and}\mspace{14mu} b_{n}} = {{{A_{n}{\sin\left( \phi_{n} \right)}}\therefore A_{n}} = {\sqrt{a_{n}^{2} + b_{n}^{2}} = {\sqrt{{A_{n}^{2}{\cos^{2}\left( \phi_{n} \right)}} + {A_{n}^{2}\;{\sin^{2}\left( \phi_{n} \right)}}} = A_{n}}}}}$where $\phi_{n} = {\tan^{- 1}\left( \frac{b_{n}}{a_{n}} \right)}$

In one scenario, the process shown in FIG. 52 was implemented for arange of sine waves according to the table below.

TABLE I NACT W Asym A₁ φ₁ A₂ φ₂ A₃ φ₃ A₄ φ₄ 2 0.33 100% 1 30° 0.5 −30° 30.25 189% 1 45° 0.71  0° 0.33 −45° 4 0.2 269% 1 54° 0.81  18° 0.54 −18°0.25 −54°

The variable “NACT” in Table I is used to define the number of sinewaves since it can also represent the number of actuators. For two sinewaves, an asymmetry of 100% can be achieved, which indicates there istwice the magnitude in the positive direction (or vice versa). Highernumbers of sine waves can provide even higher amounts of asymmetry asshown in Table I. One example is shown in FIG. 44. Other examples areshown in FIGS. 53-55.

General Synchronized Vibration can be performed with a set ofnon-sinusoidal waveforms. Even without use of Fourier synthesis,asymmetric waveforms can be generated by synchronizing the waveforms tocreate positive interference of two or more waveforms in one direction,and negative interference of two or more waveforms in the oppositedirection. Embodiments with non-sinusoidal waveforms can still have thepeaks of two or more waveforms occur simultaneously with positiveinterference in one direction and also occur simultaneously withnegative interference in the opposite direction.

FIG. 56 shows two triangular waveforms that are synchronized together.Profile 1112 a has twice the amplitude of profile 1112 b, while profile1112 b vibrates at twice the frequency of profile 1112 a. The peaks ofprofile 1112 a and 1112 b occur simultaneously, at times with positiveinterference and at times with negative interference. The combinedwaveform of profile 1112 a and 1112 b will generate an asymmetricwaveform in a similar fashion that the combined waveform in FIG. 44.

To create an especially distinct vibration effect, some LRA vibrationactuators can be operated at an amplitude high enough to push the movingmass into the travel stops, thereby creating an impact force during eachoscillation. The impact with the travel stops will generate a vibrationwaveform that is not sinusoidal. Multiple such actuators can besynchronized together to generate positive and negative interference asinstances of impacts of masses with travel stops. This configuration cangenerate sharp peaks of vibration force, where direction of vibration iscontrollable. These sharp peaks of vibrations could be used to generatehaptic sensations corresponding to impacts such as simulating the recoilof a gun. A wide range of vibration effects can be generated withnon-sinusoidal vibrations. Examples are presented herein that use sinewave vibration waveforms, with the understanding that similar approachescould be generated with other waveforms.

One waveform that can be simulated is referred to as a “missingfundamental” waveform, which takes advantage of a phenomenon of humanperception. As explained in “Music and Connectionism” by Peter M. Todd,D. Gareth Loy, MIT Press 2003, humans may perceive that a sound containspitch of a certain frequency even though that frequency is not presentin the sound if the sound contains higher frequencies that are integermultiples of the low frequency. In haptic applications, low frequencyvibrations may be difficult to generate due to size and powerconstraints, while it may be easier to generate higher frequencyvibrations. A vibration waveform can be generated that does not containa desired low frequency, but does include higher frequencies at integermultiples of the desired low frequency. A person may perceive thedesired low frequency vibration, just as they perceive the missingfundamental in a sound. The perception of a missing fundamental invibration can be enhanced by including audio or visual effects at thedesired low frequency.

The embodiment shown in FIG. 57 can generate asymmetric torques aboutthe mounting platform. A pair of LRAs 1116 a and 1116 b are mountedtowards the top of the mounting platform 1100. A second pair of LRAs1118 a and 1118 b are mounted towards the bottom of mounting platform1100. When the top pair of LRAs is operated with the same magnitude butopposite direction force than the bottom pair, a pure torque isgenerated on the mounting platform. When both the top and bottom pairvibrate with an asymmetric waveform, such as that shown in FIG. 44, thenthe torque vibration is also asymmetric and can apply a higher peaktorque in the clockwise direction than the counterclockwise direction(or vice versa). Furthermore, the amplitude of the asymmetric torquevibration may be controlled by proportionally controlling the peak forcein each LRA.

LRAs generate vibration forces along an axis and thus are described as“Linear Force Actuators.” Other Linear Force Actuators includeslider-crank vibrators, rack and pinion vibrators, linear actuators thatdo not use resonance, pistons, and solenoids. Rocking actuators andpivoting actuators (such as described in U.S. patent application Ser.No. 11/476,436) generate forces that are approximately along an axis andfor many applications can be considered Linear Force Actuators. Indeed,any embodiment described herein as employing LRAs can also beimplemented with Linear Force Actuators or other actuators that generateforces that are approximately along an axis.

A controller for General Synchronized Vibration of a pair of LinearForce Actuators is shown in FIG. 58, which could control embodimentssuch as that shown in FIG. 43. A vibration device controller generatescommands of frequency, f, commanded amplitudes, Ac, and commanded phasepc. A driver circuit generates the voltage and current that drives theactuators. The driver circuit may output a waveform of a sine wave,square wave, triangle wave, or other waveform. The actuator may generatea force waveform that is similar to the waveform output of the drivercircuit. Alternatively, the actuator may generate a force waveform thatdiffers from the waveform output of the driver circuit. For example, thedriver circuit may output a square wave but the actuator may generate aforce that is mostly a sine wave due to the physics of the actuator.

Both LRA and ERM Vibration Actuators take some time to ramp up to speedto generate their maximum force output. Embodiments described hereininclude controllers that may or may not synchronize the actuators duringthe ramp up period. In addition, a Vibration Device may be commanded totransition from one vibration effect to another vibration effect. Duringthis transition time interval, the controller may or May not synchronizethe actuators.

A vibration device controller can be a microprocessor or otherprogrammable device. For each actuator in the vibration device, thevibration device controller can modify the frequency of vibration, thephase of vibration, the amplitude of vibration, or any combination ofthese parameters. The ability to change these parameters allows for asingle vibration device to generate a wide range of waveforms.

The phase and amplitude of the force output of a Vibration Actuatordepends on both the control signal and the physical characteristics ofthe actuator. For example there is often a phase lag between the controlsignal and the force output of the actuator. To distinguish between thewaveform of the actuator outputs and the waveform of the control signal,the subscript “c” notation is used to designate the control waveform.Thus the commanded amplitudes, Ac, and the commanded phase pc are notnecessarily a direct correlation to the actual amplitude and phase ofthe actuator force. For example, the command voltage, V, of a vibrationdevice controller of an LRA actuator driven with a sinusoidal voltagesignal at a frequency ω, with a command phase of φ_(c), and a voltagepeak magnitude A_(c), given by:V=A _(c) sin(ωt+φ _(c))  (38)

However, due to the phase lag inherent in the actuator and frequencyresponse of the actuator, the steady state force output of the actuator,F_(a), may be given by:F _(a) =A sin(ωt+φ)  (39)

The phase lag is the difference between φ and φ_(c). The frequencyresponse is reflected in the ratio between A_(c) and A. Both the phaselag and the frequency response are functions of the actuator physicsthat can vary with vibration frequency, and which is often representedby an actuator specific Bode plot. For effective implementation ofsynchronized vibration it can be advantageous to take into considerationthe phase lag inherent in each vibration actuator. This can be done byadding an equal but opposite phase offset to the controller waveform sothat the actuator phase lag does not impact synchronization.

One method to implement this offset is to use a look up table, Bodeplot, or algorithm for each actuator that determines the appropriatephase offset for a given vibration frequency. In addition, it can beadvantageous to use a lookup table, Bode plot, or algorithm to determinethe required voltage magnitude needed to generated the desired vibrationforce magnitude. The Fourier synthesis approach and the approach ofmatching positive and negative peaks of vibration described herein areimplemented in reference to the actual phase of the actuator forceoutput rather than the phase of the waveform from the actuator drivecircuits. In order to simplify notation herein, the phase lag due to theactuator physics is generally not included in the equations relating tosynchronization. Rather a more compact notation is used which representsthe vibration force output, F, with the understanding that theappropriate command signal is generated to provided that output. Thecommand signal includes the necessary phase lag and magnitude adjustmentas needed based upon the actuator physics. The magnitude control can beimplemented with a voltage, current, PWM signal of voltage or current,or other type of command used to drive said actuator. The Fouriersynthesis approach and the approach of matching positive and negativepeaks of vibration describe specific target frequency and phase ofvibration for actuators within the vibration device; however, even ifthese target frequency and phase are not exactly met, the overallvibration effect often is close enough to the desired waveform toachieve a desired effect.

Due to manufacturing variations, two actuators that are built on thesame assembly line may have different physical characteristics thataffect their Bode plot, including phase lag, amplitude characteristicsor resonant frequency. In some embodiments a sensor or sensors can beused to detect the phase of an actuator, the amplitude of vibration ofan actuator, or the amplitude and phase. Such a sensor could be anoptical sensor, Hall-effect sensor or other type of sensor that detectswhen a moving mass passes the midpoint or other point of vibration. Onesuch embodiment is shown in FIG. 59, where a sensor 1128 is integratedinto to a Linear Force Actuator 1124 and detects when the moving mass1126 reaches passes a midpoint position. A sensor integrated into anactuator can provide continuous, continual or periodic measurement ofactuator performance and be used to update calibration parameters whilethe device is in use and does not require a specified calibrationperiod.

Another method of sensing is to attach actuators 1124 a and 1124 b tothe Mounting Platform 1100 of the vibration device 1134 as shown in FIG.60. This sensor 1136 could be an accelerometer or other sensor thatmeasures the combined motion or combined force of the mounting platform.

The sensor measurements can be used to self-calibrate the vibrationdevices. A test pattern can operate each actuator separately to identifythe actuator phase lag, force amplitude characteristics, and resonantfrequency. These characteristics can be used to update a lookup table,Bode plot, or algorithm used to generate the voltage commands to theactuators. The combined force of multiple actuators can also be measuredto confirm that the desired force effects are being achieved.Accordingly, the vibration device controller can use the sensormeasurements to update the commanded amplitude, phase, and frequency asshown in FIG. 61.

Embodiments of the disclosure also include configurations with multiplesets of aligned vibration actuators. One such configuration is shown inFIG. 62 that includes two sets of actuators. Set 1 consists of two LRAs1138 a and 1138 b that are both aligned with the x axis of the vibrationdevice 1134. Set 2 consists of two LRAs 1140 a and 1140 b that are bothaligned with the y axis of the vibration device. Set 1 generates forceF_(S1B1) from LRA 1138 a, and generates force F_(S1B2) from LRA 1138 b.Set 2 generates force F_(S2B1) from LRA 1140 a, and generates forceF_(S2B2) from LRA 1140 b.

In the embodiment shown in FIG. 62, the combined vibration force is thevector sum of all the vibration actuators. Using the notation of U.S.patent application Ser. No. 11/476,436, a₁ and a₂ are unit vectorsaligned with the forces from set 1 and set 2 respectively. In onecontrol approach for the embodiment shown in FIG. 62, the waveforms ofboth sets are controlled to have similar shapes but with differentmagnitudes. Magnitude coefficients are designated by the variable A,where the scalar A₁ multiplies the waveform of set 1 and the scalar A₂multiplies the waveform of set 2. The combined force vector,F_(combined), with this control approach with sinusoidal waveforms isgiven by:F _(combined) =a ₁ A ₁(B ₁ sin(ω₁ t+φ ₁)+B ₂ sin(ω₂φ₂))+a ₂ A ₂(B ₁sin(ω₁ t+φ ₁)+B ₂ sin(ω₂ t+φ ₂))  (40)

As described in U.S. patent application Ser. No. 11/476,436, there aremethods for selecting the magnitude of A₁ and A₂ that will generate adesired direction for the vector F_(combined), yet these methods mayonly specify the axis of vibration and not whether the magnitude offorce is positive or negative and thus limit the range of uniquedirection of vibrations to a range of 180 degrees. According to oneaspect of the disclosure, an embodiment allowing control of thedirection of vibration in all 360 degrees of the plane of the MountingPlatform, may have the following parameter relationships:

ω₂=2ω₁;

φ₁=0 and φ₂=−90 for a direction between −90 and +90 degrees;

φ₁=0 and φ₂=90 for a direction between 90 and 270 degrees;

A₁ and A₂ specified by equation 19 above

Numerous other embodiments are possible with multiple sets of alignedvibration actuators. Each set of aligned actuators can generate anarbitrary waveform, p_(AlignedSet). Embodiments of synchronizedvibrations created from arbitrary shaped profiles are described above.Many such embodiments show a single actuator generating each waveform.However, it is also possible to have a set of aligned actuators createthese waveforms. Therefore, such embodiments can be expanded to includeconfigurations where a set of aligned actuators take the place of asingle actuator. In these configurations, the arbitrary waveformprofiles would take the form of the arbitrary waveform, p_(AlignedSet)as discussed herein.

Accordingly, embodiments of asymmetric vibration include 3Dconfigurations and non-orthogonal configurations. An example of twonon-orthogonal LRA Pairs is shown in FIG. 63. These LRAs can generatewaveforms in desired directions throughout the xy plane. The actuatorsin each aligned set can be LRAs, rocker actuators, and other sets ofactuators that generate approximately linear forces. An equationdescribing the combined force vector for M aligned sets with all setshaving similar shaped waveforms but potentially different magnitudes isgiven by:F _(combined) =a ₁ A ₁(p _(AlignedSet))+a ₂ A ₂(p _(AlignedSet))+ . . .+a _(M) A _(M)(p _(AlignedSet))  (41)

The approaches used to determine the values of A described above can beapplied to these configurations as well. A variety of Lissajousvibration patterns are also described above, including lines, circles,ellipses, parabolas, etc. Asymmetric vibration waveforms can be used toproduce larger peak forces during one part of the Lissajous vibrationpattern than another part.

Turning to another aspect of the disclosure, an ERM is depicted in FIG.64. A basic ERM includes a motor 1204, a shaft 1208, and an eccentricmass 1206. The motor 1204 could be a DC brushed motor, a DC brushlessmotor, an AC induction motor, stepper motor, or any other device thatturns electrical energy into rotary motion. The shaft 1208 is a powertransmission element that transmits the rotary motion of the motor intorotary motion of the eccentric mass. However, alternate powertransmission methods could be any means of transmitting the rotarymotion of the motor 1204 into rotary motion of the eccentric mass 1206,such as a belt, gear train, chain, or rotary joint. The eccentric mass1206 could be any body that spins on an axis that is not coincident withits center of mass. Furthermore, the power transmission element mayinclude geometry such that the axis of rotation of the eccentric mass1206 is not necessarily coincident or parallel to the rotation axis ofthe motor 1204, and the eccentric mass 1206 does not necessarily rotateat the same angular velocity as the motor 1204.

One method of generating vibration forces is with an ERM where aneccentric mass is attached to motor shaft. As the motor rotates,centrifugal forces are generated onto the motor. General SynchronizedVibration can be applied to multiple ERMs by controlling the frequencyand phase of rotation of the eccentric masses. FIG. 65 shows oneembodiment for a vibration device 1200 that uses an arbitrary number MERMS; the first two being ERM 1210 a, 1210 b and the last being 1210 m.All ERMs are attached to a mounting platform 1202 and the combinedvibration force of the device is the vector sum from all ERMs.

For the ith ERM, A_(i) is the amplitude of the vibration force, ω_(i) isthe frequency of vibration, and φ_(i) is the phase of vibration. Thecombined vibration force of the ERMs in FIG. 65 is given in the x and ycoordinates by:F _(Ex) =A ₁ cos(ω₁ t+φ ₁)+A ₂ cos(ω₂ t+φ ₂)+ . . . +A _(M) cos(ω_(M)t+φ _(M))F _(Ey) =A ₁ sin(ω₁ t+φ ₁)+A ₂ sin(ω₂ t+φ ₂)+ . . . +A _(M) sin(ω_(M)t+φ _(M))

FIG. 66 shows one embodiment for a vibration device 1200 that uses fourERMS 1212 a, 1212 b, 1214 a, and 1214 b. All four ERMs are attached to amounting platform 1202 and the combined vibration force of the device isthe vector sum from all four ERMs.

The force and torque imparted by an ERM onto a mounting platform are dueto a combination of the centrifugal force from the rotating eccentricmass, the torque between the stator and rotor of the motor and otherinertial forces such as gyroscopic effects. As the speed of the ERMincreases the centrifugal force increases and typically becomes thedominant portion of the vibration force. Accordingly, once an ERM hassped up, the vibration force imparted by an ERM onto the mountingplatform is close to the centrifugal force imparted by the rotatingeccentric mass.

In one embodiment, the ERMs are configured in counter-rotating pairs,where each ERM in a pair has the same eccentric mass and operates at thesame angular speed but the ERMs rotate in opposite directions from eachother. FIG. 4 ERM shows such an embodiment with a first counter-rotatingpair consisting of ERM 1212 a and ERM 1212 b. The combined vibrationforce of just this first pair is given by:F _(E1x) =A ₁ cos(ω₁ t+φ ₁+σ₁)+A ₁ cos(−ω₁ t−φ ₁σ₁)F _(E1y) =A ₁ sin(ω₁ t+φ ₁+σ₁)+A ₁ sin(−ω₁ t−φ ₁+σ₁)

The phase difference between ERM 1212 a and ERM 1212 b is represented bytwo variables, φ₁ and σ₁, where φ₁ represents a temporal phase and ishalf of the difference in overall phase and σ₁ represents a geometricangle and is half of the average of the overall phase difference. For anERM the magnitude of the vibration force, A, is equal to mrω², where mis the mass, r is the radius of eccentricity, and ω is the speed ofangular rotation in radians per second. Through trigonometricidentities, this combined vibration force vector of the first ERM paircan be represented by the equation below. In this configuration, theforce from a single counter-rotating pair generates a sinusoidalvibration force aligned with an axis of force direction defined by theangle σ₁.

$\begin{matrix}{F_{E\; 1} = {2A_{1}{\cos\left( {{\omega_{1}t} + \phi_{1}} \right)}\left\lfloor \begin{matrix}{\cos\left( \sigma_{1} \right)} \\{\sin\left( \sigma_{1} \right)}\end{matrix} \right\rfloor}} & (42)\end{matrix}$

The embodiment in FIG. 66 has a second counter-rotating pair formed byERM 1214 a and ERM 1214 b, with both ERMS having the same eccentric massas each other and operating at the same angular speed as each other butin opposite directions. This second counter-rotating pair generates acombined vibration force of:F _(E2x) =A ₂ cos(ω₂ t+φ ₂+σ₂)+A ₂ cos(−ω₂ t−φ ₂+σ₂)F _(E2y) =A ₂ sin(ω₂ t+φ ₂+σ₂)+A ₂ sin(−ω₂ t−φ ₂+σ₂)

In one control method, σ₁ and σ₂ are set equal to the same value, σ, andtherefore both ERM pairs generate a vibration along the same axis andthe combined vibration force vibration force vector of all four ERMs isgiven by:

$\begin{matrix}{F_{E} = {{2A_{1}{\cos\left( {{\omega_{1}t} + \phi_{1}} \right)}\left\lfloor \begin{matrix}{\cos(\sigma)} \\{\sin(\sigma)}\end{matrix} \right\rfloor} + {2A_{2}{\cos\left( {{\omega_{2}t} + \phi_{2}} \right)}\left\lfloor \begin{matrix}{\cos(\sigma)} \\{\sin(\sigma)}\end{matrix} \right\rfloor}}} & (43)\end{matrix}$

In another control method, σ₂ is set equal to n+σ₁ and therefore bothERM pairs generate a vibration along the same axis but the contributionfrom the second ERM pair has a negative sign. With this method thecombined vibration force vibration force vector of all four ERMs isgiven by:

$\begin{matrix}{F_{E} = {{2A_{1}{\cos\left( {{\omega_{1}t} + \phi_{1}} \right)}\left\lfloor \begin{matrix}{\cos(\sigma)} \\{\sin(\sigma)}\end{matrix} \right\rfloor} - {2A_{2}{\cos\left( {{\omega_{2}t} + \phi_{2}} \right)}\left\lfloor \begin{matrix}{\cos(\sigma)} \\{\sin(\sigma)}\end{matrix} \right\rfloor}}} & (44)\end{matrix}$

There are similarities between the application of General SynchronizedVibration to Linear Force Actuators and ERMs. In both cases, thecombined vibration force can be composed of a superposition of sinewaves, and in both cases it is possible to implement asymmetricvibrations. One embodiment asymmetric vibration uses the relativemagnitudes and phases for superposition of two sinusoidal waves. In thisembodiment, the amplitude of the fundamental frequency is twice that ofthe second harmonic. For the embodiment shown in FIG. 66, aconfiguration for high asymmetry is shown in Table II below. TheGeometric Angle, σ, can be selected arbitrarily based upon the desireddirection of vibration. The eccentricity of the second ERM pair isrepresented relative to the eccentricity of the first ERM pair. Thespeed of rotation of the second ERM pair is twice the speed of rotationof the first ERM pair. It should be noted that high levels of asymmetrymay be achieved even if the values specified in Table II are onlyapproximately implemented. For example, in the case of superposition oftwo sine waves, if there is a 30% error in the amplitude of vibration,then 90% of desired asymmetry effect may still be realized.

TABLE II Centrifugal Geometric Frequency of Temporal Force Eccentric-Angle, σ Rotation Phase, φ ERM Magnitude ity (radians) (radians/sec)(radians) 1212a A₁ m₁r₁ σ  ω₁ 0 1212b A₁ m₁r₁ σ −ω₁ 0 1214a (½)A₁(⅛)m₁r₁ σ 2ω₁ 0 (or n) 1214b (½)A₁ (⅛)m₁r₁ σ −2ω₁  0 (or n)

Steps of General Synchronized Vibration are shown in FIG. 67 for thecase of a configuration shown in Table II. The time, t, is representedin terms of the period of the fundamental frequency, where T₁=2π/ω₁. Asseen in the uppermost illustration of FIG. 67, at time t=0, the forcesof all ERMs are aligned with the axis of vibration in the positivedirection, and the position of the eccentric masses are all aligned inthe same orientation. Accordingly, at t=0 the combined vibration forcehas a large magnitude. At t=T₁/4 as shown in the center illustration,the combined force vector is in the negative direction along the axis ofvibration, yet the negative magnitude is not at a peak value sincecontribution only occurs from ERM 1214 a and ERM 1214 b, while theforces from ERM 1212 a and ERM 1212 b cancel each other out. At t=T₁/2,as shown in the bottom illustration, the combined force vector is alsoin the negative direction along the axis of vibration, yet the negativemagnitude is not at a peak value since there is negative interferencebetween the first ERM pair (ERM 1212 a and 1212 b) and the second ERMpair (ERM 1214 a and 1214 b). At t=T₁/2 the forces of the first ERM pairare in the opposite direction of the forces from the second ERM pair,and the orientation of the eccentric masses of the first ERM pair is 180degrees opposite the orientation of the eccentric masses of the secondERM pair. Accordingly, asymmetric vibration is generated with a largerpeak force occurring along the positive direction aligned with the axisof vibration. As shown in Table II the temporal phase of ERMs 1214 a and1214 b can also be set to n, in which case asymmetric vibration willoccur with a larger peak force along the negative direction aligned withthe axis of vibration.

Embodiments are possible with a plurality of ERM pairs, as shown in FIG.68 which has N ERM pairs; the first two pairs being 1216 a and 1216 b,and the last pair 1216 n. In one control method the first ERM pair 1216a is rotated at a fundamental frequency, the second ERM pair 1216 b isrotated at twice the fundamental frequency, and so on through all Npairs with the Nth pair 1216 n rotating at N times the fundamentalfrequency. Using Fourier synthesis it is possible to approximate a widerange of waveforms.

In the embodiment shown in FIG. 68, each ERM within a pair can have thesame eccentricity, and each pair can be controlled so that one ERM inthe pair rotates in the opposite direction of the other ERM with thesame rotational speed. Asymmetric vibrations can be generated that havea higher peak force in a direction relative to the peak force in theopposite direction. High amounts of asymmetry can be generated using theprocess discussed above with regard to FIG. 52 (and Table I), whichspecifies magnitudes and phases for each harmonic sine wave. Themagnitude of vibration of an ERM is the product of the eccentricity, mr,and the angular velocity, ω, squared. Accordingly, the eccentricity ofthe ith ERM as a function of the relative sine wave amplitude is givenby:m _(n) r _(n)=(A _(n) /A ₁)m ₁ r ₁ /n ²  (45)

The phases may be represented relative to the starting time of aspecific waveform of pulse-trains being approximated. In someimplementations it is more convenient to set the phase of the firstharmonic to zero and represent the phases of the other harmonicsrelative to the first harmonic. An equation that converts the phase ofthe nth harmonic, φ_(n), to a phase of the nth harmonic relative to thefirst harmonic, is given by:φ_(rn)=φ_(n)−(ω_(n)/ω₁)φ₁  (46)

In addition, the phases may be defined relative a series of sine waves,while the ERM vibration equation Eq. 42 is specified in terms of acosine wave. A cosine wave is a sinusoidal wave, but the phase isshifted by 90 degrees from a sine wave. Table I shows parameters forembodiments that superimpose 2, 3, and 4 sine waves. These parameterscan be converted to relevant parameters for embodiments with 2, 3, and 4ERM pairs, using Eq. 45 and Eq. 46 along with the 90-degree shift forthe cosine representation. Table III, provided below, shows theseparameters for ERM pairs which generate high levels of asymmetry. Themethod described in FIG. 52 can be used to specify parameters for anynumber of ERM pairs.

TABLE III Number of ERM Pairs 2 3 4 Pair 1 Amplitude: A1 1 1 1 Pair 1Eccentricity m₁r₁ m₁r₁ m₁r₁ Pair 1 Relative Phase φ_(r1) 0 0 0 (degrees)Pair 2 Amplitude: A2 0.5 0.71 0.81 Pair 2 Eccentricity 0.125 m₁r₁ 0.1775m₁r₁ 0.2025 m₁r₁ Pair 2 Relative Phase φ_(r2) 180 180 180 (degrees) Pair3 Amplitude: A3 0.33 0.54 Pair 3 Eccentricity 0.0367 m₁r₁  0.060 m₁r₁Pair 3 Relative Phase φ_(r3) 270 270 (degrees) Pair 4 Amplitude: A4 0.25Pair 4 Eccentricity 0.0156 m₁r₁ Pair 4 Relative Phase φ_(r4) 0 (degrees)

Implementing General Synchronized Vibration with ERMs has an advantagethat a wide range of vibration frequencies can be generated withoutbeing restricted to a specific resonance range. As the ERM frequencyincreases the centrifugal forces increase, the ratio of waveformamplitudes of A₁ and A_(n) remains constant. Accordingly, high levels ofasymmetric vibrations can be generated with a single ratio ofeccentricity, as shown in Table II and Table III, over an arbitraryfrequency.

An embodiment with four ERMS is shown in FIG. 69. ERMS 1222 a, 1222 b,1224 a and 1224 b are stacked vertically inside a tube 1220, whichserves as the mounting platform 1202. This embodiment could be used as auser input device which is grasped by the hand, similar to how thePlayStation® Move motion controller is grasped. Configurations withstacked ERMs are convenient for a wide range of hand held devices and toapply vibration forces to a wide range of body parts.

Steps of General Synchronized Vibration are shown in FIG. 70 for thecase of a configuration shown in FIG. 69. The parts shown in FIG. 69 arethe same parts as shown in FIG. 70, but part numbers are not called outin FIG. 70. Each frame of FIG. 70 shows the eccentric masses of the ERMsand a line extending from each mass indicates the centrifugal forcevector that the mass generates. The combined force vector of all ERMs isshown by the thicker line under the ERMs. In the embodiment shown inFIG. 70 the top two ERMs 1222 a and 1224 b are rotating clockwise fromthe top view perspective, and the bottom two ERMs 1222 a and 1224 b arerotating counter-clockwise. Furthermore the top 1224 b and bottom 1224 aERMs have lower eccentric masses and are rotating at twice the frequencyof the middle two ERMs 1222 a and 1222 b.

Other embodiments are possible with different frequency and massrelationships. The time, t, is represented in terms of the period of thefundamental frequency, where T₁=2π/ω₁. As seen in FIG. 70, at time t=0,the forces of all ERMs are aligned with the axis of vibration in thepositive direction, and the position of the eccentric masses are allaligned in the same orientation. Accordingly, at t=0 the combinedvibration force has a large magnitude. At t=2T₁/8 the combined forcevector is in the negative direction along the axis of vibration, yet thenegative magnitude is not at a peak value since contribution only occursfrom ERM 1224 a and ERM 1224 b, while the forces from ERM 1222 a and ERM1222 b cancel each other out. At t=4T₁/8 the combined force vector isalso in the negative direction along the axis of vibration, yet thenegative magnitude is not at a peak value since there is negativeinterference between the first ERM pair (ERM 1222 a and 1222 b) and thesecond ERM pair (ERM 1224 a and 1224 b). At t=4T₁/8 the forces of thefirst ERM pair are in the opposite direction of the forces from thesecond ERM pair, and the orientation of the eccentric masses of thefirst ERM pair is 180 degrees opposite the orientation of the eccentricmasses of the second ERM pair. The magnitude of the combined vibrationforce is shown by the line beneath the eccentric masses at each point intime.

Another vibration device is shown in FIG. 71, in which the devicecontains two ERMs 1230 a and 1230 b attached to a mounting platform 1202that are rotating in the same direction. When the rotational speed andeccentricity of both ERMS are the same, this configuration is referredto as a Co-Rotating Pair, or “CORERM Pair”. The center between the ERMeccentric masses is referred to as the center of the COREMR Pair. Whenthe angle between the two ERMs is kept at a fixed value of angle, c, theCORERM Pair generates a combined centrifugal force that is equivalent toa single ERM. However, the magnitude of centrifugal force of the CORERMPair is a function of the angle c. When c is equal to zero the combinedforce magnitude is twice that of a single ERM and when c is equal to 180degrees then the centrifugal force magnitude is equal to zero sincethere is no overall eccentricity. Accordingly, when c is close to 180degrees, the centrifugal force may not be the dominant force output ofthe CORERM Pair. Instead, gyroscopic or torque effects may take on alarger proportion of the force and torques applied onto the VibrationDevice. Where A is the magnitude of force from just one of the ERMs inthe pair, ω is the rotational speed, and φ is the phase of rotation,then the combined vibration force generated by a CORERM Pair is givenby:

$\begin{matrix}{F_{CORERM} = {2A\;{{{\cos(c)}\begin{bmatrix}{\cos\left( {{\omega\; t} + \varphi} \right)} \\{\sin\left( {{\omega\; t} + \varphi} \right)}\end{bmatrix}}.}}} & (47)\end{matrix}$

A single vibration device could operate similar to ERMs as eithercounter-rotating pairs or co-rating pairs. There are a number ofadvantages of operating a vibration device in a mode where some of theERMs function as CORERMs. One advantage is that the magnitude ofvibration can be increased by using a CORERM pair. Another advantage isthat legacy vibration effects can be generated that simulate a singleERM rotating. For example, a haptic interface could be operated at onetime to generate asymmetric vibration forces and at another time tosimulate a single ERM. If users are accustomed to haptic signals from asingle ERM, the CORERM pair allows for such familiar effects to begenerated.

A large number of co-rotating ERMs could by synchronized together inwith no phase offset such that their force magnitudes combine to createa vibration effect similar to a single large ERM. If all the co-rotatingERMs are CORERM pairs with co-located centers, then the center for thecombined force would be the same as for a single large ERM.

Another advantage of using CORERM pairs is that they allow for Fouriersyntheses of a wider range waveforms. One such embodiment is to replaceeach ERM in FIG. 66 with a CORERM pair, which is shown in FIG. 72. ERM1212 a, 1212 b, 1214 a, and 1214 b in FIG. 66 correspond to CORERM 1232a, 1232 b, 1234 a, and 1234 b in FIG. 72. Such an embodiment would besimilar to the original configuration of FIG. 66, but where themagnitude of centrifugal force from each ERM could be adjustedindependently of the speed of rotation (by adjusting the angle c withinCORERM pairs). Fourier synthesis allows arbitrary waveforms to beapproximated with a superposition of sine waves where the amplitude,phase, and frequency of the sine waves can be adjusted. With asufficiently large number of CORERM pairs, any waveform with a zero-DCoffset could be approximated. The embodiment in FIG. 72 also allows thedirection of vibration to be controlled.

Control of amplitude of vibration force can be especially useful inasymmetric vibrations used for haptic applications. A vibration devicecan be grasped by one hand, two hands, held with other body parts,attached to any body part, or placed in contact with any body part.Generally at least two sides of a haptic vibration device are in contactwith a user, and each side contacts the user at somewhat differentlocations on their body. These different locations could be thedifferent sides of a grip of a tube vibration device, such as shown inFIG. 69.

Human perception often requires that a threshold be exceeded before asensory event is perceived. In one embodiment, the magnitude of anasymmetric waveform is adjusted so that on one side of a VibrationDevice low vibration forces are generated that are below a threshold ofperception and on the opposite side higher peak forces are generatedthat are above a threshold of perception. In this manner, a vibrationforce may be perceived on mostly one location that is in contact withthe vibration device, even though the vibration device is in contactwith a number of locations on the body. As the direction of vibration isvaries, the location on the body at which vibration is perceived mayalso vary. This approach uses vibration to generate effects that arevary significantly according to the direction of vibration, and thus areuseful for indicating directional cues.

An embodiment with 2 ERMs in a tube is shown in FIG. 73. In FIG. 73A theERMs 1222 a and 1222 b are mounted close to the center of the tube 1220and thereby reduce the torque vibration that is due to the distancebetween the ERMs. One way of controlling this configuration is tooperate the ERMs in a counter-rotating mode and generate force in aspecified direction, with only a small torque vibration so as tominimize distraction from the force effect. In FIG. 73B the ERMs 1222 aand 1222 b are mounted close to the ends of the tube 1220 and therebyincrease the torque vibration that is due to the distance between theERMs. One way of controlling this configuration is to operate the ERMsin a counter-rotating mode and generate force in a specified direction,while simultaneously generating a large torque vibration effect.

The embodiment in FIG. 69 can also be operated with CORERM pairs. ERMs1224 a and 1224 b can form one pair, and ERMs 1222 a and 1222 b can formanother pair. When both of these CORERM pairs are rotating in the samedirection and have a 180 phase difference, there will be no net force ornet torque on the vibration device. However, this embodiment will createa gyroscopic effect with minimal force or torque vibrations. Thisimplementation could be used to generate the sensation of moving a swordor a heavy mass in a video game or other type of simulation.

The forces between an ERM and a mounting platform include bothcentrifugal forces and the motor torque generated between the motorstator and rotor. When an ERM is rotating at operating speed, thecentrifugal forces are typically large and dominate the effect from themotor torque. However, some embodiments can bring effects from the motortorque to the forefront. When two ERMs with parallel axes are operatedas a co-rotating pair with a phase offset of 180 degrees, the twoeccentric masses balance each other out and the centrifugal forcescancel each other out. In this embodiment, the torque about the axes ofrotation can be felt more prominently. The torque about the axis ofrotation is felt during the acceleration and deceleration of therotating masses. Higher torques can often be generated by periodicallyreversing the applied voltage to the motor, since the electromagneticforce (back EMF) in the motor can add to the reverse voltage beingapplied.

Even higher torques about the axis of rotation can be generated by usinga brake to cause a sudden deceleration to a rotating mass. This approachis known as a reaction-wheel method for generating torques, and isuseful when there is no grounded actuator to apply a torque effect. FIG.74 shows an eccentric mass 1206 configured for use as a reaction wheel.A rim 1242 is attached to the eccentric mass 1206, and creates a surfacefor a brake 1244 to contact. When the brake 1244 is actuated arelatively high torque can be generated. The reaction-wheelconfiguration is another example of the wide range of effects thatGeneral Synchronized Vibration can generate. A single vibration devicecan have ERMs that are operated in counter-rotating modes, co-rotatingmodes, and as reaction-wheels.

One embodiment of an ERM Pair uses interleaved masses, an example ofwhich is shown in FIG. 75. In this embodiment, the shapes of theeccentric masses are implemented so that the masses can be interleavedwithin one another yet still rotate independently. With interleavedMasses, both ERMs can share the same axis of rotation. In addition, amass distribution can be implemented such that the eccentric forcesshare the same plane (which can be indicated by the height in the sideview in FIG. 75). Each ERM in the pair has a rotating mass that includesboth an eccentric component, and a symmetric component such as themotor's rotor. The center of mass of the eccentric mass refers to thecenter of mass of only the eccentric component of the rotating mass. Thecenter of mass of the eccentric mass rotates about the axis of rotationof the ERM, yet its position can be projected (in a linear algebrasense) onto a single point on the axis of rotation. With interleavedmasses the geometry and density of the eccentric masses can be selectedsuch that the center of mass of the eccentric masses from both ERMs areprojected onto the same position on the axis of rotation. In thisconfiguration the eccentric forces from both ERMs share the same plane.In FIG. 75, ERM1 1250 a, contains a motor 1252 a and an eccentric mass1254 a which is shaped with a semi-circle cross section, and ERM2 1250b, contains a motor 1252 b and an eccentric mass 1254 b which is shapedwith an arc cross-section. Other shapes of eccentric masses are possiblethat allow for independent rotation of two masses.

In an embodiment with interleaved masses, the ERM pair can generatecentrifugal forces without generating a torque due to the distancebetween the ERMs. Interleaved ERM pairs are useful for generating pureforce vibrations without torque vibrations. Interleaved ERM pairs can beoperated as a co-rotating pair, and thereby vary the amplitude ofvibration independently from the frequency of vibration. A co-rotatinginterleaved pair can switch between a 180 degree angle between the ERMsand a 0 degree angle to rapidly turn the vibration effect on or off.Since there are no torque effects, the complete vibration sensation willbe turned off when the ERMs have a relative phase angle of 180 degrees.In addition, such a configuration can generate a gyroscopic effectwithout generating torque vibrations.

An interleaved ERM pair can also be operated as a counter-rotating pair,and thereby generate a vibration force along an axis. By controlling thephase of the interleaved ERMS, the direction of the vibration force canbe controlled.

Embodiments with 3 ERMs are shown in FIGS. 76A-B. In FIG. 76A, amounting platform 1202 shaped as a tube, holds a center ERM, 1312, anERM 1314 a is located above the Center ERM, and an ERM 1314 b is locatedbelow the center ERM. All 3 ERMs are aligned such that their axis ofrotation is collinear. In this figure, the dimension A is the distancealong the axis of rotation between the projection of the center of therotating eccentric mass of ERM 1312 onto the axis of rotation and theprojection of the center of the rotating eccentric mass of 1314 a ontothe axis of rotation. In a similar fashion, ERM 1314 b is located suchthat it is at a distance B along the axis of rotation between theprojection of the center of its eccentric mass onto the axis of rotationand that of the projection of the center of the rotating eccentric massof ERM 1312 onto the axis of rotation. Furthermore, the ERMs 1314 a and1314 b can be synchronized to operate at the same frequency and samephase, which will generate a combined force centered along the axis ofrotation.

When the distance A times the eccentricity of ERM 1314 a is equal to thedistance B times the eccentricity of ERM 1314 b, then the combinedvibration force from synchronized ERMs 1314 a and 1314 b is projectedonto the axis of rotation at the same point along this axis that thecenter of the eccentric mass of ERM 1312 is projected onto. In thisconfiguration the combined vibration force from all 3 ERMs share thesame plane. With this configuration, a vibration force can be generatedby all 3 ERMs without generating a torque. Accordingly, the embodimentwith 3 ERMs in FIG. 76A can be operated in a mode where it isfunctionally similar to the embodiment with 2 ERMs shown in FIG. 75, butthe embodiment in FIG. 76A uses standard shaped eccentric masses. Theembodiment in FIG. 76A can be operated in a co-rotation mode, where all3 ERMs rotate in the same direction and with the same frequency. ERMs1314 a and 1314 b can be operated with the same phase, and this phasecan be adjusted relative to the phase of the center ERM, 1312, whichwill modulated the amplitude of the vibration force.

If the eccentricity of ERM 1314 a plus the eccentricity of ERM 1314 b isequal to the eccentricity of ERM 1312, then complete cancellation of thevibration forces can occur when all 3 ERMs are rotating. This completecancellation allows for rapid on and off control of vibration forces.The embodiment in FIG. 76A can also be operated in a counter-rotationmode, where the direction of rotation and phase of ERMs 1314 a and 1314b are the same, yet the center ERM, 1312, is operated in the oppositedirection. In the counter-rotating mode, vibration forces along an axiscan be generated, and the direction of the vibration can be controlledby modulation the relative phase of the ERMs. The embodiment in FIG.76A, also can be operated in a mode that is not similar to theinterleaved embodiment in FIG. 75; here, the center ERM can be turnedoff and ERM 1314 a can be operated out of phase with ERM 1314 a tocreate a rocking torque in the device. In addition, each ERM in FIG. 76Acan be operated at a different frequency. ERMs with smaller eccentricmasses often can be operated at higher top frequencies, and thereby theembodiment in FIG. 76A can create even a wider range of vibrationeffects.

Another embodiment with 3 ERMs is shown in FIG. 76B. A mounting platform1202 shaped as a tube holds a center ERM, 1312, an ERM 1314 a is locatedabove the center ERM, and an ERM 1314 b is located below the center ERM.All 3 ERMs are aligned such that their axis of rotation is collinear. InFIG. 76B, the dimension A is the distance along the axis of rotationbetween the center of the rotating eccentric mass of ERM 1312 and thecenter of the rotating eccentric mass of 1314 a. ERM 1314 b is locatedat the same distance A along the axis of rotation between its center ofthe rotating eccentric mass and that of the center of the rotatingeccentric mass of ERM 1312.

When the eccentricity of ERMs 1314 a and 1314 b are half theeccentricity of the center ERM 1312, and the ERMs 1314 a and 1314 b aresynchronized to operate at the same frequency and same phase, thencomplete cancellation of vibration forces and torques can occur at aphase offset of 180 degrees. Thus, the embodiment in FIG. 76B can havethe same functional advantages as the embodiment in 76A. A furtheradvantage of the embodiment of FIG. 76B is that two ERMs have identicalspecifications and thus can be more easily manufactured.

An additional embodiment with 3 ERMs is shown in FIG. 77. A mountingplatform 1202, holds a center ERM, 1312, an ERM 1314 a is located to oneside of the center ERM, and an ERM 1314 b is located to the other sidethe Center ERM. All 3 ERMs are aligned such that their axes of rotationare parallel. When all 3 ERMs are rotating in the same direction, theembodiment in FIG. 77 can create similar vibration effects as theembodiments in FIGS. 76A-B; the frequency off all 3 ERMs can be thesame, the phase of ERMs 1314 a and 1314 b can be the same, and therelative phase with the center ERM 1312 will determine the magnitude ofthe vibration force.

To provide complete cancellation of the vibration force, theeccentricity of the rotating mass of ERMs 1314 a and 1314 b can beselected to be half that of the center ERM 1312. Complete cancellationof vibration torques can occur in the co-rotating mode when the centerERM 1312, is located in the center between ERMs 1314 a and 1314 b. Theembodiment in FIG. 77 can also be operated in a counter-rotating mode,where the ERMs 1314 a and 1314 b rotate in the same direction with thesame phase, and the center ERM 1312 rotates in the opposite direction.This counter-rotating mode provides a vibration force along an axis, andthe direction of the vibration force can be controlled by the phases ofthe ERMs. However, in the embodiment in FIG. 77, there will be avibration torque during the counter-rotating mode since the axes of theERMs are not collinear.

The embodiment in FIG. 77 can also be operated in a counter-rotatingmode, where the ERMs 1314 a and 1314 b rotate in the same direction withthe same phase, and the Center ERM 1312 rotates in the oppositedirection. This counter-rotating mode provides a vibration force alongan axis, and the direction of the vibration force can be controlled bythe phases of the ERMs. However, in the embodiment in FIG. 77, therewill be a vibration torque during the counter-rotating mode since theaxes of the ERMs are not collinear.

General Synchronized Vibration of ERMS requires control of both thefrequency and phase of rotating eccentric masses. One method is to use amotor, such as a stepper motor, where the position and speed can bedefined open-loop by specifying a desired series of steps. Anothermethod is to use closed loop control with a sensor or sensors thatmeasure frequency and phase. An ERM with a sensor 1260 is shown in FIG.78. The sensor 1262 can be a continuous position sensor that measuresthe position of the eccentric mass at frequent intervals. Continuoussensors could be encoders, potentiometers, a Hall Effect sensor thatdetects a series of gear teeth or other feature of a rotating object, orother types of position sensors. The velocity of the eccentric masscould be calculated from the time interval between subsequent rotations,through taking the derivative of position measurements, or directlythrough use of a tachometer.

Another method to sense frequency and phase is to use a discrete sensorthat detects when the motor shaft spins by a set position relative tothe motor housing, or a number of set positions relative to the motorhousing. Such discrete sensors can use reflective optical sensors thatreflect off a rotating object coupled to the motor shaft, line-of-sightoptical sensors that detect when a rotating object coupled to the motorshaft interrupts the line of site, hall effect sensors that detect adiscrete component that is coupled to the rotating shaft, or othermethod of discrete detection of the shaft position.

FIG. 79 shows an ERM with a reflective optical sensor 1264 which detectslight reflecting off an eccentric mass 1206. A light source 1268, suchas an LED, is shining onto the pathway of the eccentric mass 1206. Whenthe eccentric mass 1206 rotates by the sensor 1266, light reflects offthe eccentric mass 1206 into the light sensor 1266. For each rotation ofthe eccentric mass 1206 the light sensor 1266 will detect when theeccentric mass 1206 comes into the range of the sensor 1266 and beginsto reflect light, and when the eccentric mass 1206 leaves the range ofthe sensor 1266 and stops to reflect light. The velocity of the ERM 1264can be determined between the intervals of each rotation, such as thetime when the eccentric mass 1206 begins to reflect light. Alternativelythe velocity of the ERM 1264 can be calculated by the duration of timethat the eccentric mass 206 reflects light. The phase of the eccentricmass 1206 can be determined by the timing of a specific event such asthe rising or, falling edge of the light sensor 1266 which correspondsto the time when the eccentric mass 1206 begins and stops reflectinglight.

FIG. 80 shows an ERM with a line-of-sight optical sensor 1270. The lightsensor 1266 detects when the eccentric mass 1206 interrupts the lightpath. A light source 1268, such as an LED, is shining onto the pathwayof the eccentric mass 1206. When the eccentric mass 1206 rotates throughthe light path, the sensor 1266 detects the interruption. FIG. 81 showsan ERM with a Hall Effect sensor 1272. The Hall Effect sensor 1274 istriggered when the eccentric mass 1206 rotates by.

Implementing General Synchronized Vibration with ERMs requires that thefrequency and phase be controlled for each ERM that is used tosynthesize the desired waveform. Both the frequency, ω, and phase, φ,can be controlled by controlling the position, θ, of the rotating shaftof the ERM to be at a desired position as a function of time.Accordingly, control of frequency and phase can also be equivalent tocontrol of the position of an eccentric mass to a desired positiontrajectory over time. Measurement of the shaft position can be performedcontinuously or at discrete instances such as when the shaft passes acertain position. Continuous measurements could be made with an encoderor other type of sensor that measures positions at frequency intervals.Discrete measurements could be made with an optical sensor that detectswhen the eccentric mass passes by. Discrete measurements could be madeat a single position of motor rotation or at multiple positions.Discrete measurements can be augmented with a second sensor that alsomeasures the direction of rotation. A direction sensor could be a secondoptical sensor mounted close to the first optical sensor. The directionof rotation can be determined by which optical sensor is triggeredfirst.

A wide range of methods can be used for real-time control the positionand speed of an ERM. One method is Proportional-Integral-Control.Another method includes time optimal control as described by “OptimalControl Theory: An Introduction”, by Donald E. Kirk, Dover Publications2004. One real-time control approach is presented below for controllinga set of synchronized ERMs. The approach is written for use with adiscrete sensor, but can also be applied with a continuous sensor. Whena continuous sensor is used, the dynamic performance of the system canbe improved by more accurately updating the commands to the motorcontinuously.

An exemplary control approach for a system with M ERMs is now discussed.For each ERM for i=1 to M, define the desired frequency, ω_(des, i), anddesired phase, φ_(des, i). The desired direction of rotation is definedas dir_(des, i)=sign(ω_(des, i)). Initialize the following variables:

-   -   a. Time, t=0    -   b. Number of revolutions of each ERM, nrev_(i)=0 (for all i)

Next, start motors turning by providing an open-loop command, V_(open)_(—) _(loop, i) to each ERM corresponding to the desired frequency,ω_(des, i). The open-loop command can be determined by the motor'storque-speed curve and correspond to the voltage that will generate aterminal velocity as the desired value. An optional startup operation isto turn on the motors at a high or maximum voltage to reduce the startuptime. Since sensors exist to detect speed of rotation, the voltage canbe reduced to a desired level when the ERMs reach an appropriate speed.In this fashion the sensors used for synchronization can also be used toreduce the startup time of the overall vibration device. As each ERMpasses its discrete sensor:

-   -   c. Measure the time and record: t_(meas, i)=t    -   d. Calculate the desired position at the measured time:        θ_(des,i)=ω_(des,i) t _(meas,i)+φ_(des,i)    -   e. Calculate the measured position, θ_(meas, i) at the measured        time:        -   Increment the number of revolutions: nrev_(i)=nrev_(i)+1            θ_(meas,i)=2πdir_(i) nrev_(i)+θ_(sensor) _(—) _(offset,i)        -   θ_(sensor) _(—) _(offset, i) is based upon the mounting            location of the discrete sensor, and is often equal to zero.        -   dir_(i) is the actual direction of the ERM rotation.            Typically the ERM will be rotating in the direction of the            initial open-loop command. However, it is also possible to            use a second sensor input to measure the direction of            rotation, or use the time history of the motor command to            calculate the direction.    -   f. Calculate the error in position, θ_(error, i), for each ERM:        θ_(error,i)=θ_(des,i)−θ_(meas,i)

A control law may be implemented to reduce the position error of eachERM. There are a wide range of control of control approaches in thefield of control, including:

-   -   g. Proportional, Integral, Derivative (“PID”) based upon the        calculated error in position. The command to the motor would be:        V _(com,i) =K _(p,i)θ_(error,i) +K _(I,i)∫θ_(error,i) dt+K        _(D,i) dθ _(error,i) /dt    -   h. Use the open-loop command as a baseline command to the ERM,        since it is based upon the motor's characteristics, and apply        PID to correct for remaining errors. The command to the motor        would be:        V _(com,i) =V _(open) _(—) _(loop,i) +K _(p,i)θ_(error,i) +K        _(I,i)∫θ_(error,i) dt+K _(D,i) dθ _(error,i) /dt        -   The use of the open-loop command can reduce the need for a            large integral control gain, and improve dynamic            performance.    -   i. State-space control approach. The physical state of each ERM        is a function of both its position and velocity. Each time an        ERM passes its discrete sensor, the speed of revolution can be        calculated from the time interval since the last sensor        measurement. The state-space approach uses both the position and        velocity to determine an appropriate control signal. For the        durations where no sensor measurements are made, a state        observer can be used to estimate the motor's position and speed,        where the model of the state observer is based upon the physical        properties of the motor and rotating mass.    -   j. Use bang-bang control, which operates the motor at maximum        forward command and maximum reverse commands for specified        durations of time. For example, if an ERM is operating at the        correct speed but position has a phase lag, then the motor        should be accelerated for a duration of time and then        decelerated back to the original speed for a second duration of        time. A physical model of the motor dynamics can be used to        determine the appropriate durations of acceleration and        deceleration.

With all control approaches a bidirectional or unidirectional motordriver could be used. An advantage of using bidirectional motor driversis that high levels of deceleration can be applied to an ERM by applyinga reverse voltage, even if the motor never changes direction ofrotation. This approach can reduce the time it takes to synchronize theERMs. Another advantage of using bidirectional motor drivers is thatERMs could be operated in both counter-rotating and co-rotating modes.

An alternative method of calculating the position error is discussedbelow. Where the desired force is represented by Ai sin(ωit+φi) and thedesired position is represented by θ_(i)(t)=ω_(i)t+φ₁, start all ERMs atopen loop voltages corresponding to ω_(i). Let the motors spin up tospeed when ERM 1 passes the sensor so that it starts in phase, thenreset the timer so t=0. See Table IV below

TABLE IV Control of ERM Time at θ θ θ Change which sensor measureddesired desired in θdes is triggered (θ_(meas)) (θ des) Δ t (θ_(des))(Δθdes) Δθ_(meas) θ_(error) t₁ 0 ωt₁ + φ θ_(des) − θ_(meas) t₂ 2π ωt₂ +φ t₂ − t₁ ωΔt + 2π θ_(error) = θ_(des) _(—) _(prev) θ_(error) _(—)_(prev) + Δθ_(des) − Δθ_(meas) t₃ 4 π ωt₂ + φ t₃ − t₂ ωΔt + θ_(des) − 2πθ_(des) _(—) _(prev) θ_(des) _(—) _(prev)

In a digital system, ERM control may include the following. First, setrotation counts per revolution (e.g., 256 or 512). Correct for timeroverflow so Δt=t_(i)−t_(i-1) is always correct. Define ω in terms ofrotation counts per timer counts. And use interrupts (or otheroperations) to avoid missing when an ERM passes by a sensor.

Some embodiments of Synchronized Vibration Devices can be controlledsuch that the combined force and torque sum to zero. In such anembodiment the force and torques from individual Vibration Actuatorsbalance each other out to generate a net zero force and torque. Anadvantage of such an embodiment is that Vibration Actuators can bebrought up to speed and put into a mode when no vibration effects aregenerated. When vibration effects are desired, they can be quicklyimplemented by modifying the phase of the vibration, without the lag forbringing the actuators up to speed. This embodiment is referred to as“Spinning Reserve”, and is analogous to the same term used for kineticenergy in an electric utility power plant that is held in reserve toquickly provide power when needed. The spinning reserve approach allowsvibration to be quickly turned on and off. Spinning Reserve embodimentscan include ERM actuators that are spinning in such a manner that thecombined forces and torque sum to zero. Spinning Reserve embodiments canalso include with LRA actuators and other resonant actuators that arevibrating in such a manner that the combined forces and torque sum tozero.

The spinning reserve approach has the advantage of fast on and offresponse times, but also can require increased power consumption sincethe vibration actuators are operated even when no overall vibrationeffects are generated. To reduce the added power consumption, thevibration actuators can be spun up to speed at the first indication thata need for vibration force is imminent. Such indications could be akeystroke, computer mouse motion, user touching a touch-screen, movementdetection via a sensor of a game controller, beginning of a game portionwhere vibration effects are used, or any other event that would indicatethat a desired vibration effect would be imminent. In a similar fashionpower can be conserved by spinning down and stopping the actuators oncethe need for vibration is no longer imminent. Indications to spin downthe actuators could include passage of a set amount of time where nouser input is registered, transition to a new phase of a computerprogram where vibration effects are no longer needed, or otherindication. During the spin up and spin down of the actuators, theactuators can by synchronized so that they operate in a spinning reservemode and do not generate a combined vibration force. In this fashion,the user will not feel the spin up and spin down of the vibrationactuators.

A spinning reserve embodiment with 4 ERMs is shown in FIG. 82.Synchronized Vibration can be applied to the embodiment shown in FIG.82, where the combined forces and torque cancel each other out. In onesuch embodiment the eccentricity and rotational inertia of ERMs 1190 a,1190 b, 1192 a and 1192 b are equal to each other. In one such controlmethod all 4 ERMs rotate in the same direction. The frequency and phasecould be as shown in Table V below. The synchronized phases within a setof ERMs, can be controlled relative to each other and not just relativeto absolute time. Accordingly, the phases shown in Table V and othertables in this document only represent one set of phases in absolutetime that achieve the described effect. Other phase combinations canachieve similar effects.

TABLE V ERM 1190a ERM 1192a ERM 1192b ERM 1190b Frequency ω ω ω ω Phase−90° 90° 90° −90°

FIG. 83 shows the forces of the ERMs from Table V as the ERMs progressthrough time, wherein each row of images illustrates one time slice (8slices in all). The parameters for frequency and phase shown in Table Vcorrespond to the force vectors shown in FIG. 83. In a similar fashionother configurations and control methods of vibrations devices can alsobe simulated.

Another method of Synchronized Vibration can be applied to theembodiment shown in FIG. 82, where the combined forces and torque canceleach other out. In such a control method ERM 1190 a rotates in theopposite direction of ERM 1190 b, and ERM 1192 a rotates in the oppositedirection of ERM 1192 b. The frequency and phase could be as shown inTable VI.

TABLE VI ERM 1190a ERM 1192a ERM 1192b ERM 1190b Frequency ω ω −ω −ωPhase −90° 90° 90° −90°

When ERMs are rotating they generate a gyroscopic effect due to theangular inertia of the motor rotor and rotating mass. When the angularvelocity of the ERMs is large this gyroscopic effect can be used togenerate a haptic sensation in response to changes in orientation of thevibration device. The implementation of spinning reserve as shown inTable V has a gyroscopic effect since all ERMs are rotating in the samedirection and their angular inertia combined. The implementation ofspinning reserve as shown in Table VI does not have a gyroscopic effectsince half the ERMs are rotating in the opposite direction of the otherhalf, and therefore angular inertias cancel each other out whenrotational inertias are equal. The mode of implementation of spinningreserve can be selected according to the desired gyroscopic effect.

Another method of Synchronized Vibration can be applied to theembodiment shown in FIG. 82, where the combined forces generate a forcealong the x axis and the torques cancel each other out. The frequencyand phase could be as shown in Table VII.

TABLE VII ERM 1190a ERM 1192a ERM 1192b ERM 1190b Frequency ω −ω −ω ωPhase 0° 0° 0° 0°

Another method of Synchronized Vibration can be applied to theembodiment shown in FIG. 82, where the combined forces generate a forcealong the y axis and the torques cancel each other out. The frequencyand phase could be as shown in Table VIII.

TABLE VIII ERM 1190a ERM 1192a ERM 1192b ERM 1190b Frequency ω −ω −ω ωPhase 90° 90° 90° 90°

Indeed Synchronized Vibration can be applied to the embodiment shown inFIG. 82, where the combined forces generate a force along any axis inthe XY plane. The control that implements an axis at 30 degree and thetorques cancel each other out is shown in Table IX.

TABLE IX ERM 1190a ERM 1192a ERM 1192b ERM 1190b Frequency ω −ω −ω ωPhase 30° 30° 30° 30°

Another method of Synchronized Vibration can be applied to theembodiment shown in FIG. 82, where a combined torque is generated andthe forces cancel each other out. One such pure torque embodimentgenerates equal amplitudes torque in the clockwise and counterclockwisedirections, and is referred to as a symmetric torque implementation. Thefrequency and phase that generates a symmetric torque could be as shownin Table X.

TABLE X ERM 1190a ERM 1192a ERM 1192b ERM 1190b Frequency −ω ω −ω ωPhase −90° −90° 90° 90°

Another implementation of pure torque can produce an asymmetric torque,where the peak torque in the clockwise direction is larger than the peaktorque in the counterclockwise direction, or vice versa. One suchasymmetric torque implementation for a 4 ERM configuration could be asshown in Table XI. This is achieved by operating ERMs 1192 a and 1192 bat twice the frequency of ERMs 1190 a and 1190 b, and controlling thephase appropriately. For the configuration shown in FIG. 82, when allERMs have the same eccentricity, the amount of asymmetry in the torquecan be increased by placing ERMs 1192 a and 1192 b at a distance of ⅛thfrom the center relative to the distances of ERMs 1190 a and 1190 b.

TABLE XI ERM 1190a ERM 1192a ERM 1192b ERM 1190b Frequency ω 2ω 2ω ωPhase −90° −90° 90° 90°

Yet another method of Synchronized Vibration can be applied to theembodiment shown in FIG. 82, where all ERMs rotate together and forcesdo not cancel each other out. This implementation generates an effect ofone large ERM that would have the eccentricity of all ERMs combined. Thefrequency and phase that generates a symmetric torque could be as shownin Table XII.

TABLE XII ERM 1190a ERM 1192a ERM 1192b ERM 1190b Frequency ω ω ω ωPhase 0° 0° 0° 0°

A wide range of haptic effects can be generated by switching between thevarious effects described herein. When the ERMs are rotating at the samespeed in two different effects, the change between effects (includingthe no-vibration spinning reserve) can be achieved quickly. In manycases the change in effect only requires a positive or negative phasechange of 90 degrees in specific ERMs.

Embodiments with 4 ERMs that are not aligned along the same axis alsocan generate many useful effects. Fig. DIAMOND_OF_(—)4ERMS shows anembodiment of 4 ERMs. When this embodiment is implemented with 4 ERMswith the same eccentricity, a spinning reserve effect can be generatedwith same frequency and phases shown in Table V. In FIG. 84 the centerof ERM pair 1194 a and 1194 b, have the same center as ERM pair 1196 aand 1196 b. Indeed, any embodiment with 2 pairs of ERMs that share thesame center can be controlled in a spinning reserve mode.

The embodiment shown in FIG. 84 can also be controlled to generate apure force vibration along a specified direction, where the torquescancel each other out. The same frequency and phase as shown in TableVII, Table VIII, and Table IX can be used. A symmetric torque can begenerated with this embodiment as well, but with a frequency and phaseas defined in Table V, and replacing ERMs 1190 a, 1190 b, 1192 a, and1192 b with ERMs 1194 a, 1194 b, 1196 a, and 1196 b, respectively.

As discussed above with regard to FIG. 75, interleaved ERM pairs may beemployed according to aspects of the disclosure. Another embodiment ofan interleaved ERM pair is shown in FIGS. 85A-B. As shown in FIG. 85A,an inner eccentric mass 1320 a is driven by motor 1322 a and an outereccentric mass 1320 b is driven by motor 1322 b. The outer eccentricmass 1320 b is shaped so that the walls get thicker going away from themotor 1322 b. This extra thickness compensates for the material requiredfor structural support of the eccentric mass near the motor. As shown inthe side view of FIG. 85B, the inner eccentric mass 1320 a fills thevoid inside eccentric mass 1320 b. The result is that both eccentricmasses 1320 a and 1320 b share the identical center of mass, whicheliminates unwanted torque effects.

Another embodiment of an interleaved ERM pair is shown in FIGS. 86A-C.Here, an inner eccentric mass 1330 a is driven by motor 1332 a and anouter eccentric mass 1330 b is driven by motor 1332 b. The end ofeccentric mass 1330 a that is furthest from the motor 1332 a issupported by a bearing 1334 b, which is installed into eccentric mass1330 b. The end of eccentric mass 1330 b that is furthest from the motor1332 b is supported by a bearing 1334 a, which is installed intoeccentric mass 1330 a. The bearings 1334 a and 1334 b allow for thespinning eccentric masses 1330 a and 1330 b to be supported on bothends. This allows the eccentric masses 1330 a and 1330 b to spin fasterwithout deflection due to cantilever loads, and helps reduce friction inthe motors 1330 a and 1330 b.

The performance of almost any vibration device can be improved byapplying the methods and embodiments of General Synchronized Vibrationdiscussed herein. This approach toward synchronization allows for a widerange of waveforms to be generated including asymmetric waveforms thatgenerate larger peak forces in one direction than the opposingdirection. Applications range from seismic shakers and fruit treeharvesters, to vibratory feeders and miniature vibration applications.The embodiments described herein can replace more expensive actuationdevices that are used to generate complex waveforms of vibrations. Suchapplications include seismic shakers that are simulating specificearthquake profiles, and voice coils that are used to generate complexhaptic effects.

Haptic applications described herein can be used to augment any devicethat has a visual display including computer gaming, televisionincluding 3D television, a handheld entertainment system, a smartphone,a desktop computer, a tablet computer, a medical device, a surgicalinstrument, an endoscope, a heads-up display, and a wristwatch.Implementation of haptic feedback within a system that has a visualdisplay is shown in FIG. 87.

As described herein, Vibration Force cues can be generated in specificdirections, and these directions can be chosen to correspond todirection that is relevant to an object or event that is being shown ona graphic display. FIG. 88 shows a graphic display with an image thathas a direction of interest specific by an angle σ. The Vibration Deviceshown in FIG. 88 can generate haptic cues in the same direction toprovide multi-sensory input and enhance the overall user experience.

Moreover, it is be useful to generate haptic cues of directionality forapplications where a person does not have visual cues, such as to guidea blind person or applications where vision is obscured or preoccupiedwith another task. For example, if a person had a handheld device suchas a mobile phone that could generate directional haptic cues throughvibration, and the mobile phone knew its absolute orientation as it wasbeing held and the orientation the person should be in to move forwardto a goal, then the mobile phone could communicate directional hapticcues through vibration (a force, a torque, or a combined force andtorque) that corresponded to the direction and magnitude of the changein orientation the person holding the mobile phone needed to make.

The Vibration Devices describe herein can be used to improve theperformance of existing devices that use vibration. For examplevibration is used in fruit tree harvesting. By allowing the operator togenerate complex waveforms and control the direction of vibration ahigher yield of ripe fruit could be harvested, while leaving unripefruit on the tree. Vibratory feeders are used in factory automation, andtypically involve a significant amount of trial an error to achieve thedesired motion of the parts. By allowing the operator to generatecomplex waveforms and control the direction of vibration it can beeasier to generate the desired part motion and a wider range of partscould be processed with vibratory feeders.

The Vibration Devices described herein allow for a wide and continuousadjustment in areas such as vibration magnitude, frequency, anddirection. To improve performance of a Vibration Device, sensor feedbackcan be used, as shown in FIG. 89. With this approach a Vibration Deviceapplies forces onto an object, and a sensor measures a feature orfeatures of the object. The sensor information is provided to theVibration Device Controller, which can then modify the vibrationwaveform to improve overall system performance. One area of applicationcould be a vibratory parts feeder, where a sensor measures the rate atwhich parts move along a pathway, and the waveform is modified toimprove the part motion. Another area of application could bepreparation and mixing of biological and chemical solutions. A sensorcould measure the effectiveness of the mixing and the vibrationwaveforms could be adjusted accordingly.

One application is to use General Synchronized Vibration for locomotion.FIG. 90 shows an embodiment where a Vibration Device 1200 rests on asurface 1282. There exists friction between the surface 1282 and theVibration Device 1200. Accordingly, motion of the Vibration Device 1200will only occur if a force parallel to the surface 1282 exceeds afriction threshold. In this embodiment, an asymmetric waveform is beinggenerated so that the peak positive force exceeds the friction thresholdand the peak negative force is less than the friction threshold.Accordingly in each vibration cycle the Vibration Device 1200 can bepushed in the positive x direction when the peak force in the positive xdirection exceeds the friction threshold.

However, there will generally be no motion in the negative x direction,since the friction threshold is not exceeded. In this fashion, theVibration Device 1200 will take steps in the positive x direction. Thedirection of motion along the x axis can be reversed by changing thesynchronization of the Vibration Actuators and generating an asymmetricwaveform that has a larger peak force in the negative direction. Alocation device can be made to move in arbitrary directions on a surface1282 by using a Vibration Device 1200 where the direction of vibrationcan be controlled on a plane, such as those shown in FIG. 62 and FIG.66. In a similar fashion a locomotion device can be made to rotate bygenerating asymmetric torque vibrations, such as the one shown in FIG.57.

Vibration is also used for personal pleasure products such asJimmyjane's Form 2 Waterproof Rechargeable Vibrator. Vibration is alsoused for personal massager products such as the HoMedics® Octo-Node™Mini Massager. Vibration is also used for beauty products such as EstéeLauder's TurboLash and Lancôme's Ôscillation mascara applicators. INOVAproduces the AHV-IV Series Vibrators for Vibroseis seismic exploration.General Synchronized Vibration can be used to improve the performance ofsuch products by allowing the user to customize the vibration waveformsand direction of peak vibration forces.

General Synchronized Vibration may also be used in therapeutic medicalapplications. For example a Vibration Device could vibrate a patient'sstomach to aid in digestion, and the patient or a sensor could determinehow to adjust the vibration over time.

Although aspects of the disclosure have been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent disclosure. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present disclosure as defined by the appended claims. By way ofexample only, it is possible to vary aspects of the embodiments hereinto some degree while achieving General Synchronized Vibration and otherbenefits of the disclosure. For instance, the frequency of vibration,amplitude of vibration, profile or waveform of vibration, phase ofvibration, timing of vibration, alignment of actuators, rigidity of thevibration device, rigidity of the attachment between the actuators andthe vibration device, and design and control parameters may all beadjusted, either independently or in any combination thereof.

The invention claimed is:
 1. A vibration device, comprising: a mountingplatform; and a plurality of actuators, each of the plurality ofactuators being configured to build up an amplitude of that actuator'sforce output over successive cycles of operation; wherein each of theplurality of actuators is attached to the mounting platform so the forceoutputs of the plurality of actuators are superimposed onto the mountingplatform, and the plurality of actuators is configured to simultaneouslygenerate force waveforms, corresponding to the force outputs, for atleast two different harmonics of a desired force output waveform suchthat each actuator generates a single harmonic of the desired outputwaveform, wherein each harmonic is a non-zero integer multiple of thefundamental frequency.
 2. The vibration device of claim 1, wherein eachof the plurality of actuators is selected from the group consisting of alinear resonant actuator, an eccentric rotating mass actuator, apivoting actuator, and a rocking actuator.
 3. The vibration device ofclaim 1, wherein the at least two different harmonics include a firstharmonic of the desired output waveform.
 4. The vibration device ofclaim 1, wherein the at least two different harmonics include a secondharmonic of the desired output waveform.
 5. The vibration device ofclaim 1, wherein the at least two different harmonics include a thirdharmonic of the desired output waveform.
 6. The vibration device ofclaim 1, further comprising a controller coupled to the plurality ofactuators to control an amplitude of the desired output waveform.
 7. Thevibration device of claim 1, wherein the vibration device is configuredto generate haptic directional cues.
 8. The vibration device of claim 1,wherein: the vibration device is arranged in a handheld electronicdevice selected from the group consisting of a remote control, a gamecontroller, and a watch, and the vibration device is configured togenerate one or more haptic effects for the handheld electronic device.9. The vibration device of claim 8, wherein the game controller isselected from the group consisting of a driving game controller and amotion game controller.
 10. The vibration device of claim 1, wherein theat least two different harmonics do not include a first harmonic of thedesired output waveform.
 11. A vibration device, comprising: a mountingplatform; and a plurality of actuators, each of the plurality ofactuators being configured to build up an amplitude of that actuator'sforce output over successive cycles of operation; wherein each of theplurality of actuators is attached to the mounting platform so the forceoutputs of the plurality of actuators are superimposed onto the mountingplatform, and the plurality of actuators is configured to simultaneouslygenerate force waveforms, corresponding to the force outputs, for atleast two different harmonics of a desired force output waveform suchthat each actuator generates a single harmonic of the desired outputwaveform; wherein two of the plurality of actuators comprise interleavedeccentric rotating masses arranged so the two actuators are individuallycontrollable by a controller to simultaneously generate non-zero forceoutputs such that the superimposed force outputs of the two actuatorssum to substantially zero force and substantially zero torque.
 12. Avibration device, comprising: a mounting platform; a plurality ofeccentric rotating mass actuators, each of the plurality of eccentricrotating mass actuators attached to the mounting platform; and acontroller coupled to the plurality of eccentric rotating mass actuatorsto independently control a frequency and a phase of each eccentricrotating mass actuator to simultaneously generate force waveforms for atleast two different harmonics of a desired force output waveform suchthat each eccentric rotating mass actuator generates a single harmonicof the desired output waveform, wherein each harmonic is a non-zerointeger multiple of a fundamental frequency.
 13. The vibration device ofclaim 12, wherein a frequency, direction and relative phase between eachof the eccentric rotating mass actuators are controlled by thecontroller to produce a combined vibration force along a predeterminedaxis.
 14. The vibration device of claim 13, wherein the combinedvibration force along the predetermined axis is asymmetric.
 15. Avibration device, comprising: a mounting platform; a plurality ofeccentric rotating mass actuators, each of the plurality of eccentricrotating mass actuators attached to the mounting platform; and acontroller coupled to the plurality of eccentric rotating mass actuatorsto independently control a frequency and a phase of each eccentricrotating mass actuator; wherein: the plurality of eccentric rotatingmass actuators includes two pairs of eccentric rotating mass actuators,each pair being aligned and attached to the mounting platform such that:the first pair of eccentric rotating mass actuators is configured tocounter-rotate at a first rotational frequency f1 to produce a firstlinear vibrating force, and the second pair of eccentric rotating massactuators is configured to counter-rotate at a second rotationalfrequency f2 to produce a second linear vibrating force, the secondrotational frequency f2 being an integer multiple of the firstrotational frequency f1, so that a combined linear vibration forcewaveform on the mounting platform generated by operation of the twopairs of eccentric rotating mass actuators is asymmetric.
 16. Thevibration device of claim 15, wherein axes of revolution of eacheccentric rotating mass actuator of the two pairs of eccentric rotatingmass actuators are substantially parallel.
 17. The vibration device ofclaim 15, where the two pairs of eccentric rotating mass actuators arecontrolled by the controller to generate centripetal forces such thatthe first linear vibrating force, when the first pair is operating atthe first rotational frequency f1, is substantially twice the secondlinear vibrating force when the second pair is operating at the secondrotational frequency f2.
 18. The vibration device of claim 15, whereinaxes of revolution of each eccentric rotating mass actuator of the twopairs of eccentric rotating mass actuators are collinear.
 19. Thevibration device of claim 15, wherein centripetal force vectors of eacheccentric rotating mass actuator of the two pairs of eccentric rotatingmass actuators are coplanar.
 20. The vibration device of claim 15,wherein the controller is configured to generate haptic directional cuesusing the two pairs of eccentric rotating mass actuators.
 21. Avibration device, comprising: a mounting platform; a plurality ofeccentric rotating mass actuators, each of the plurality of eccentricrotating mass actuators attached to the mounting platform; and acontroller coupled to the plurality of eccentric rotating mass actuatorsto independently control a frequency and a phase of each eccentricrotating mass actuator; wherein: relative phases between the pluralityof eccentric rotating mass actuators are controlled by the controller tocancel out centripetal forces generated by each of the eccentricrotating mass actuators; and torques generated by the centripetal forcesby each of the eccentric rotating mass actuators cancel each other out.22. A vibration device, comprising: a mounting platform; a plurality ofeccentric rotating mass actuators, each of the plurality of eccentricrotating mass actuators attached to the mounting platform; and acontroller coupled to the plurality of eccentric rotating mass actuatorsto independently control a frequency and a phase of each eccentricrotating mass actuator each eccentric rotating mass actuator configuredto generate a single harmonic of a desired output waveform, wherein eachharmonic is a non-zero integer multiple of a fundamental frequency;wherein: the plurality of eccentric rotating mass actuators includes afirst eccentric rotating mass actuator and a second eccentric rotatingmass actuator, the first and second eccentric rotating mass actuatorshaving the same eccentricity; and the controller is configured tooperate the first and second eccentric rotating mass actuators at thesame frequency and the same phase relative to other eccentric rotatingmass actuators in the plurality of eccentric rotating mass actuators.23. A vibration device, comprising: a mounting platform; a plurality ofeccentric rotating mass actuators, each of the plurality of eccentricrotating mass actuators attached to the mounting platform; and acontroller coupled to the plurality of eccentric rotating mass actuatorsto independently control a frequency and a phase of each eccentricrotating mass actuator; wherein: the plurality of eccentric rotatingmass actuators comprises a first eccentric rotating mass actuator havinga first axis of rotation, and a second eccentric rotating mass actuatorhaving a second axis of rotation, the first and second axes beingcollinear; the first eccentric rotating mass actuator has a firsteccentric mass with a center of eccentricity at a first positionprojected onto the first axis of rotation; the second eccentric rotatingmass actuator has a second eccentric mass with a center of eccentricityat a second position projected onto the second axis of rotation; and adistance between the first and second positions is substantially zero.24. A vibration device, comprising: a mounting platform; a plurality ofeccentric rotating mass actuators, each of the plurality of eccentricrotating mass actuators attached to the mounting platform; and acontroller coupled to the plurality of eccentric rotating mass actuatorsto independently control a frequency and a phase of each eccentricrotating mass actuator; wherein: the plurality of eccentric rotatingmass actuators comprises a first eccentric rotating mass actuator havinga first axis of rotation, a second eccentric rotating mass actuatorhaving a second axis of rotation, and third eccentric rotating massactuator having a third axis of rotation, the first, second and thirdaxes being collinear; the first eccentric rotating mass actuator has afirst eccentric mass with a center of eccentricity at a first positionprojected onto the first axis of rotation; the second eccentric rotatingmass actuator has a second eccentric mass with a center of eccentricityat a second position projected onto the second axis of rotation; thethird eccentric rotating mass actuator has a third eccentric mass with acenter of eccentricity at a third position projected onto the third axisof rotation; and a distance between the first position and the secondpositions times the second eccentricity is equal to a distance betweenthe first position and the third position times the third eccentricity.25. The vibration device of claim 22, wherein the eccentricity of thefirst eccentric mass is equal to the second eccentricity plus the thirdeccentricity.
 26. A vibration device, comprising: a mounting platform; apair of linear resonant actuators arranged in parallel and attached tothe mounting platform, each linear resonant actuator including amoveable mass; and controller coupled to the pair of linear resonantactuators, the controller being configured to control a first one of thelinear resonant actuators to impart a first sinusoidal vibration forceof a first frequency f1 onto the mounting platform, and to control asecond one of the linear resonant actuators to impart a secondsinusoidal vibration force of a second vibration frequency f2 onto themounting platform, the second frequency f2 being an integer multiple ofthe first frequency f1; wherein the controller is further configured tocontrol amplitudes and angular phases of the first and second sinusoidalvibration forces to generate a combined vibration waveform that isasymmetric, wherein the angular phases may range from 0 to 360 degrees.27. The vibration device of claim 26, wherein the first and secondlinear resonant actuators are each operable over a range of frequenciesincluding resonant frequencies of the second linear resonant actuators.28. The vibration device of claim 27, wherein the resonant frequency ofthe second linear resonant actuator is tuned to be an integer multipleof the resonant frequency of the first linear resonant actuator.
 29. Thevibration device of claim 26, wherein the vibration device is configuredto generate haptic directional cues using the first and second linearresonant actuators.
 30. The vibration device of claim 26, wherein thevibration device is configured to produce haptic effects that correspondto one or more computer-generated visual events.
 31. The vibrationdevice of claim 26, wherein the vibration device is arranged in ahandheld controller, and the vibration device is configured to generateeffects for the handheld controller.
 32. The vibration device of claim26, wherein the vibration device is arranged in a device wearable by auser, and the vibration device is configured to generate haptic effectsfor the wearable device.
 33. The vibration device of claim 26, whereinthe vibration device is part of a navigation device for navigating auser from waypoint to waypoint.